Lojban (IPA /ˈloʒban/) is a constructed human language based on predicate logic.
It started to be developed in 1987 by The Logical Language Group (LLG) intending to realize Loglan's purposes as well as to further complement the language to be more usable and freely available (as indicated by its official full English name "Lojban: a realization of Loglan"). After a long initial period of debating and testing, its baseline completed by 1998 with the publication of The Complete Lojban Language.
The name "Lojban" is a combination of loj and ban, which are the short forms of logji (logic) and bangu (language) respectively. Due to its name, Lojban is sometimes misunderstood to be within some exclusive domains such as formal logic or computer programming, while it is perfectly human usable in daily conversation. While it is meant to be capable of handling highly logical concepts, it is also highly flexible to an unparalleled degree. To whatever degree the speaker wishes, it can resemble its natural, programming, or other constructed counterparts, and it can be poetic, ambiguous, precise, or neutral.
The principal sources of its basic vocabularly was the (at the time) six most widely-spoken languages: Arabic, Chinese, English, Hindi, Russian, and Spanish, in order to reduce the unfamiliarity or strangeness of the root words to people of diverse linguistic backgrounds. Some Lojbanists acknowledge that the language has drawn on other constructed languages' components, a notable instance of which is Láadan's set of indicators. Also Toki Pona and Esperanto have mutuality with Lojban to some extent.
In this article, explanations of its grammartical aspects will mostly be based on The Complete Lojban Language, and as for the orthography the Latin alphabet mode will be used.

History
Lojban has a predecessor, Loglan, a language invented by James Cooke Brown in 1955 and developed by The Loglan Institute. Loglan was originally conceived as a means to examine the influence of language on the speaker's thought (an assumption known as Sapir Whorf hypothesis).
As Brown started to claim copyright on the language's components, restraint was laid on the community's activity. In order to circumvent such control, a group of people decided to initiate a separate project, departing from the lexical basis of Loglan and reinventing the whole vocabulary, which led to the current lexicon of Lojban. In effect they established in 1987 The Logical Language Group, based in Washington DC. They also won a trial over whether they could call their version of the language "Loglan".

Origin (1955-1987)

Initial development (1987-1997)
Following the publication of The Complete Lojban Language, it was expected that "the documented lexicon would be baselined, and the combination of lexicon and reference grammar would be frozen for a minimum of 5 years while language usage grew". As scheduled, this period, which has officially been called the "freeze", expired in 2002. The speakers of Lojban are now free to construct new words and idioms, and decide where the language is heading.

The "freeze" period (1997-2002)
Lojban still shares many of the characteristics of Loglan:

Has a grammar that is based on predicate logic, designed to express complex logical constructs precisely.
Has no irregularities or ambiguities in spelling and grammar (although word derivation relies on arbitrary variant forms). This gives rise to high intelligibility for computer parsing.
Is designed to be as culturally neutral as possible.
Allows highly systematic learning and use, compared to most natural languages.
Possesses an intricate system of indicator which effectively communicate contextual attitudes or emotions.
Does not have simplicity as a design criterion. Post-foundation (2002-)
Lojban is considered to be an advantageous intellectual device for creative writing and is deemed to have many potential aspects yet to be discovered or explored.
Dan Parmenter: The removal of grammatical ambiguity from modification [...] seems to heighten creative exploration of word combination. [...] Other areas of possible benefit are (surprisingly in a 'logical' language) emotional expression. Lojban has a fully developed set of metalinguistic and emotional attitude indicators that supplant much of the baggage of aspect and mood found in natural languages, but most clearly separate indicative statements from the emotional communication associated with those statements. This might lead to freer expression and consideration of ideas, since stating an idea can be distinguished from supporting that idea. The set of possible indicators is also large enough to provide specificity and clarity of emotions that is difficult in natural languages. John Cowan: There is marker for "figurative speech" which would be used on "back stabber" and would signal "There is a culturally dependent construction here!" The intent is not that everything is instantly and perfectly comprehensible to someone who knows only the root words, but rather that non-root words are built up creatively from the roots. Thus "heart pain" would refer to the literal heart and literal pain; what would be ambiguous would be the exact connection between these two. Is the pain in the heart, because of the heart, or what? But "heart pain" would not be a valid tanru for "emotional pain", absent the figurative speech marker. Computer Network Discussions on Loglan/Lojban and Linguistics: Lojban as seen by the linguistics and cognitive science community 20, 23
The language was built to attempt to remove some limits on human thought; these limits are not understood, so that the tendency is to try to remove restrictions whenever we find the language structure gets in our way. You definitely can talk nonsense in Lojban. Bob LeChevalier: In Lojban, a little grammar makes for a lot of semantic fun, since the grammar doesn't interfere with the semantic quibble you love. [...] In addition to its grammar, Lojban is definitely a priori in its words[...] We presume that everything can be covered as compounds of the classification scheme implied by the gismu. [...] We haven't, though, tried to impose a system on the universe like most a priori languages have. Instead, we have tried to broaden gismu flexibility so that multiple approaches to classifying the universe are possible. Our rule is that any word have one meaning, not that any meaning have one word. There is no 'proper' classification scheme in Lojban. [...] Lojban offers a new world of thought. Why Lojban?
See also the proposed fourth tense of Lojban discussed by Arthur Protin, Bob LeChevalier, Carl Burke, Doug Landauer, Guy Steele, Jack Waugh, Jeff Prothero, Jim Carter, and Robert Chassell, as well as ZAhO tenses, the concepts which "average English speakers won't recognize" because most of them (the concepts) "have no exact English counterpart".
Like most languages with few speakers, Lojban lacks much of an associated body of literature and its creative extensions have not been fully realized (the true potential of its attitudinal system, for example, is considered to unlikely be drawn out "until and unless we have children raised entirely in a multi-cultural Lojban-speaking environment" have pointed out the lack of certain terms for mathematics and geometry (although this demand may now be disputed as the current set of Lojban vocabulary do actually allow the speakers to express such notions as steradian (stero), trigonometric tangent (tanjo), multiplicative inverse (fa'i), matrix transpose (re'a) among a number of other kinds of operators or metric units). Other instances which necessitate the speakers to construct noncanonical words:

Alice in Wonderland by the English-Irish author Lewis Carroll
One Thousand Nights and a Night (a classic Arabic tale)
The Moon is a Harsh Mistress (Chapter 1) by the science fiction writer Robert A. Heinlein
The Prophet by the Lebanese-American writer Kahlil Gibran
The Little Things by the short story writer/poet Raymond Carver
The Man and the Snake by the short story writer/satirist Ambrose Bierce
The Book by the cosmic horror writer H. P. Lovecraft
The Legend of Zelda (a classic NES fantasy game) by Nintendo
Eaton Interface: a translation of the Helen Eaton concept list into Lojban.
Parliamentary Rules: Lojban terms for parliamentary actions.
Lojban Adventure: a Lojban version of the classic Colossal Cave text adventure game.
There are few (almost non-existent) entries of African country names on the official list of root words while the other country names (especially those with large populations of speakers of the six source languages) are covered to a remarkable extent.
Such distinction as between palne (tray) and palta (plate) or such peculiar kind of terms as nilda'ibandu ("armor class", used in role playing games) exist while no distinction between "illustration" and "photography" is made by the available set of gismu (that is, no exclusive root word for "photography" exist but the generic pixra) (see also - Grammar: Morphology: brivla: gismu). Literature and vocabulary development
Apart from the actual practice of the language, some members of the community and LLG have been endeavoring to create various aids for the learners. The Complete Lojban Language, the definitive word on all aspects of Lojban, is one of them, finalized in 1997. Some of the projects in varying stages of completeness are:
(see also - External link: Learning Courses/Resources)
A dedicated Lojban popup dictionary as a Firefox add-on has been suggested, but is still in the level of speculation as the present lexing and parsing system of Lojban does not cover JavaScript.

Phrasebook: Lojbanic Phrasebook Project, CVS/Wiki Lojban Phrasebook, Pocket Dictionary
Parser: Lojban Parser/Machine Grammar (by Robin Lee Powell), jbofi'e (by Richard Curnow), valfendi (by Pierre Abbat)
Database: jbovlaste (by Robin Lee Powell), Reference Database (by Matt Arnold on DabbleDB)
Others: Lojban/Logic book and webpage (by John Clifford), TLI Loglan Interface (by Steven Belknap and Bob LeChevalier) Learning aids development
Currently, Lojban's learning resources available on the internet cover mainly those speakers of English, French, Spanish, Russian, Hebrew, and Esperanto, to varying degrees.
Disproportion in the community population is still noticeable. It is reasonably hoped among Lojbanists that more people from different cultural/linguistic backgrounds join the community in order to maintain and further complement the intended neutrality of the language. (see also - Community)

Community development
While the initial aim of the Loglan project was to investigate the Sapir–Whorf hypothesis, the active Lojban community recognizes additional goals for the language to be attained in the future, including:

General research into linguistics
Research in artificial intelligence and machine understanding
Improved human-computer communication, storage ontologies, and computer translation of natural language text
Use of language as an educational tool Grammar
Lojban has 6 vowels and 21 consonants. Some of them have, apart from the preferred/standard sounds, permitted variants intended to cover dissimilitude in pronunciation by speakers of different linguistic backgrounds.
There are also 16 diphthongs (and no Triphthongs). Distinction between diphthongs and monophthongs can be made by inserting a comma in the Latin alphabet mode.
The sounds may be allophoned.
For those who, given their native language background, may have trouble pronouncing (certain) consonant clusters, there is the option of inserting buffer vowels between them, as long as they differ sufficiently from the phonological vowels and are pronounced as short as possible. The resulting added syllables are completely ignored by the grammar, including for the purposes of stress determination.

Phonology
Lojban may be written in different orthography systems as long as it meets the required regularities and unambiguities. Some of the reasons for such elasticity would be as follows:
Some Lojbanist extends this principle so as to claim that even an original orthography of the language is to be sought.
This article will use the common Latin alphabet mode.

Lojban is rather defined by the phonemes (spoken form of words), therefore, as long as they are correctly rendered so as to maintain the Lojbanic audio-visual isomorphism, a representational system can be said to be an appropriate orthography of the language;
Lojban is meant to be as culturally neutral as possible, so it is never crucial or fundamental to claim that some particular orthography of some particular languages (e.g. the Latin alphabet) should be the dominant mode. Orthography
Lojban has 3 word-classes: predicate words, structure words, and name words. Each of them has uniquely identifying properties, so that one can unambiguously recognize which word is of which part of speech in a string of the language. They may be further divided in sub-classes. There also exists a special fragmental form assigned to some of the words, from which longer words can be compounded.

Morphology
According to What Is Lojban?, the language's grammatical structures are "defined by a set of rules that have been tested to be unambiguous using computers", which is in effect called the "machine grammar". Hence the characteristics of the standard syntactic (not semantic) constructs in Lojban:
Such standards, however, are to be attained with certain carefulness:
It is important to note that new Lojbanists will not be able to speak 'perfectly' when first learning Lojban. In fact, you may never speak perfectly in 'natural' Lojban conversation, even though you achieve fluency in the language. No English speaker always speaks textbook English in natural conversation; Lojban speakers will also make grammatical errors when talking quickly. Lojbanists will, however, be able to speak or write unambiguously if they are careful, which is difficult if not impossible with a natural language. Nick Nicholas and John Cowan. 'What Is Lojban? II.3
The computer-tested, unambiguous rules also include grammar for 'incomplete' sentences e.g. for narrative, quotational, or mathematical phrases.
Lojbanic expressions are modular; smaller constructs of words are assembled into larger phrases so that all incorporating pieces manifest as a possible grammatical unity. This mechanism allows for simple yet infinitely powerful phrasings; "a more complex phrase can be placed inside a simple structure, which in turn can be used in another instance of the complex phrase structure".
Its typology can be said to be basically Subject Verb Object and Subject Object Verb. However, it can practically be anything:
Such flexibility has to do with the language's intended capability to translate as many expressions of natural languages as possible, based on a unique positional case system. The meaning of the sentence {mi prami do} is determined by {prami} realizing, with its own predefined "place structure", a specific semantic relation between {mi} and {do}; when the positional relation between {mi} and {do} changes, the meaning of the sentence changes too. As shown above, Lojban has particular devices to preserve such semantic structure of words while altering their order.
As benefits to a logical language, there is a large assortment of logical connectives. Such conjunction words take different forms depending on what they connect, another reason why the (standard) Lojbanic expressions are typically precise and clear.
Multiple predicate words may be linked up together so as to narrow the semantic scope of the phrase. In skami pilno "computer user(s)", the modifying word skami narrows the sense of the modified word pilno to form a more specific concept (in which case the modifier may resemble English adverbs or adjectives).

each word has exactly one grammatical interpretation;
the words relate grammatically to each other in exactly one way.
mi prami do (SVO)
mi do prami (SOV)
do se prami mi (OVS)
do mi se prami (OSV)
prami fa mi do (VSO)
prami fe do fa mi (VOS) Syntax and semantics

Samples

Common expressions

pei .o'ucu'i [?] [relaxation!] [neutral] Are you no longer in pain?
mi nelci ko I is-fond-of you-[imperative] Make me be fond of you!
le cukta be'u cu zvati ma that-which-is-described-as book [need!] is-at what Where's the book? I need it!
ko ga'inai nenri klama le mi zdani you-[imperative] [me-the-social-inferior!] inside-type-of come that-which-is-described-as having-to-do-with-me house I would be honored if you would enter my residence.
le nanmu cu ninmu one-or-more-specific-things-which-I-describe as "men" are women The man is/are a woman/women.
seri'agi mi jgari lei djacu gi mi jgari le kabri With-physical-effect I grasp the-mass-of water, I grasp the cup. *Therefore I grasp the water, I grasp the cup. Some unique Lojbanic expressions

lo'u lu le la li'u le'u
le crisa srasu cu rirci crino
tisna fa la tsani le cnita tsina lo tinci tinsa
la bab. zbasu loi bakyzbabu loi bakygrasu
mi na djuno le du'u klama fa makau la makaus. makau makau makau Tongue Twisters
doi cevrirni.iu noi zvati le do cevzda do'u fu'e .aicai .e'ecai lo do cmene ru'i censa .i le do nobli turni be la ter. ku se cfari .i loi do se djica ba snada mulno vi'e le cevzda .e .a'o la ter. .i fu'e .e'o ko dunda ca le cabdei le ri nanba mi'a .i ko fraxu mi loi ri zu'o palci .ijo mi fraxu roda poi pacyzu'e xrani mi .i ko lidne mi fa'anai loi pacyxlu .i ko sepri'a mi loi palci .i .uicai ni'i loi se turni .e loi vlipa .e loi mi'orselsi'a cu me le do romei fa'o

xekri je blanu nicte (help·info) (a Lojbanic poem)
The Lord's Prayer Others

Community
The activities of Lojban speakers are mostly via the Internet:

Lojban.org: A user-maintained site, attempting to reflect a cross section of the Lojban community outside of the LLG.
Lojban IRC (irc.freenode.net #lojban): Based on the Freenode IRC network. One may use a web interface as an alternative to IRC clients.
Lojban Mailing List: A beginner-oriented means to talk/learn about the language.
jbovlaste: An official, dictionary editing interface created by Jay Kominek, updated by Robin Lee Powell. People can post new Lojbanic words with definitions and examples, or vote for such experimental words.
jbobac: A web-based forum that has posts/threads made up mainly of sound files.
samxarmuj/The Lojban Moo: A multi user virtual environment, similar to the old text adventure games. A guide is given here.
le jbopre pe lj's Journal: A communal Lojban blog.
lojban-valsi: A-word-a-day mailing list on the Yahoo! Groups.
uikipedias: The Lojban Wikipedia, where discussions may be conversed in English. The Internet
Gatherings of Lojbanists have been organized in USA annually since as early as 1990, called Logfest. It is mostly informal, taking place in weekend, with the only scheduled activity being the annual meeting of the LLG. Those who cannot be present may still be involved via IRC. Activity may be whatever the people who attend want to do: Lojban conversation, lessons, technical discussions, or socializing.

The Logfest
The number of Lojban speakers in total is unknown.
According to Lojban.org that, as of August 2007, some people from following countries are interested in or enthusiasts of the language:
It is generally noticed that there is little participation from Hindi peoples, in spite of the etymological nature of Lojban vocabulary.
Below are some of the notable personalities who have contributed to the development of Lojban:

Australia, Israel, United States
Argentina, Canada, China, Estonia, France, Germany, Holland, Ireland, Mexico, New Zealand, Norway, Russia, Thailand, Ukraine, United Kingdom, Venezuela.
Bob LeChevalier (aka lojbab): the president of the LLG.
John Cowan: the author of The Complete Lojban Language.
Jorge Llambías (aka xorxes): one of the most active Lojbanists, having done several translations. He is also a prominent figure on the mailing list, helping the beginners with the language.
Matt Arnold (aka epkat): one of the most active Lojbanists. He has been contributing to the translation project and software development.
Nick Nicholas (aka nitcion): an Australian linguist. He is the first fluent Lojban speaker (although he insists that he was the second, he is known to be excessively modest). He has done a lot of Lojbanic writing, including Lojban For Beginners coauthored by Robin Turner.
Robin Lee Powell (aka camgusmis): the current webmaster of Lojban.org. He provides the machine and bandwidth from which the site is served. He has also written several Lojbanic materials including a novel-sized story.
Robin Turner: a British philosopher and linguist living in Turkey. He is the coauthor of Lojban For Beginners. Population

Comparison with other constructed languages
The current number of Lojban speakers, although incalculable, does not likely equal to that of Esperanto. However, the successfulness of Esperanto as a constructed language is by no means incomparable to that of Lojban. Esperanto's leading edges have been:
Some of the contrastive points between Esperanto and Lojban are as follows.
Some of the similarities may be that both Esperanto and Lojban are difficult to achieve fluency. Aside from the purely technical linguistic aspects Esperanto and Lojban has different goals and differs greatly in which elements are considered most important. The differences in design clearly reflect this. Simplicity was a major issue for esperantos design, while it was not a goal when Lojban was designed.
The ex-Esperantist Lojbanist Nick Nicholas observes:
Since a great many Lojbanists studied Esperanto before coming to Lojbanistan, there is little overt rivalry (except on the vexing 'Sixteen Rules' issue...). The situation can be considered as a case of complementarity: International Auxilliary Language claims are renounced in order to focus on issues which simply don't exist in Esperanto. And yet we have the STS discussion on the mailing list right now... This seems to be primarily an artifact of the peculiar situation of Esperanto in America: the idealism of Esperanto, and the feel for a need for an IAL, do not have as much resonance in America as elsewhere, so there are proportionally many more people who would consider learning either Esperanto or Lojban only as a conlang. (Few outside the Anglo-Saxon world, I suspect [...] would learn Esperanto only as a conlang.) For that reason, the two languages are being compared by some (e.g. prospective students asking for comparisons on the mailing list) rather more directly than others (e.g. Esperantists or ex-Esperantists like me) may have expected, in terms of non-IAL specific issues like unambiguity or euphony.
See also: Esperanto as an international language

the larger community, more institutions, and more (alleged) native speakers;
the rich body of literature.
Esperanto words are mostly European-oriented. Lojban has a wider range of lexical etymologies.
Esperanto grammar is more apposite to usage by European people. Lojban syntax is capabe of dealing with expressions in various natural languages and is enough systematic/clear to be easily parsed by computers (i.e. it is either human- or machine-oriented).
Esperanto is often criticized for its sexism: the generic form of words is used for males while a derived form is used for females. Lojban morphology does not undergo any of such a prejudice: the marking of gender is always optional.
Typing Esperanto requires some special typesetting. Lojban can be typed by any ordinary computer keybords Esperanto
Loglan is now a generic term that refers both to James Cooke Brown's Loglan, and all languages descended from it. Since the organization that Dr. Brown established, The Loglan Institute (TLI), still calls its language Loglan, it is necessary to state that this section refers specifically to the TLI language, instead of the entire family of languages.
The principal difference between Lojban and Loglan is one of lexicon. A Washington DC splinter group, which later formed The Logical Language Group, LLG, decided in 1986 to remake the entire vocabulary of Loglan in order to evade Dr. Brown's claim of copyright to the language. After a lengthy battle in court, his claim to copyright was ruled invalid. But by then, the new vocabulary was already cemented as a part of the new language, which was called Lojban: A realization of Loglan by its supporters.
The closed set of five-letter words was the first part of the vocabulary to be remade. The words for Lojban were made by the same principles as those for Loglan; that is, candidate forms were chosen according to how many sounds they had in common with their equivalent in some of the most commonly spoken languages on Earth, which was then multiplied by the number of speakers of the languages with which the words had letters in common. The difference with the Lojban remake of the root words was that the weighting was updated to reflect more recent numbers of speakers for the languages. This resulted in word forms that had fewer sounds taken from English, and more sounds taken from Chinese. For instance, the Loglan word norma is equivalent to the Lojban word cnano (cf. Chinese 常, pinyin cháng), both meaning "normal".
Grammatical words were gradually added to Lojban as the grammatical description of the language was made.
Loglan and Lojban still have essentially the same grammars, and most of what is said in the Grammar section above holds true for Loglan as well. Most simple, declarative sentences could be translated word by word between the two languages; but the grammars differ in the details, and in their formal foundations. The grammar of Lojban is defined mostly in the language definition formalism YACC, with a few formal "pre-processing" rules. Loglan also has a machine grammar, but it is not definitive; it is based on a relatively small corpus of sentences that has remained unchanged through the decades, which takes precedence in case of a discrepancy.
There are also many differences in the terminology used in English to talk about the two languages. In his writings, Brown used many terms based on English, Latin and Greek, some of which were already established with a slightly different meaning. On the other hand, the Lojban camp freely borrowed grammatical terms from Lojban itself. For example, what linguists call roots or root words, Loglanists call primitives or prims, and Lojbanists call gismu. The lexeme of Loglan and selma'o of Lojban has nothing to do with the linguistic meaning of lexeme. It is a kind of part of speech, a subdivision of the set of grammatical words, or particles, which loglanists call little words and lojbanists cmavo. Loglan and Lojban have a grammatical construct called, metaphor and tanru, respectively; this is not really a metaphor, but a kind of modifier-modificand relationship, similar to that of a noun adjunct and noun. A borrowed word in Loglan is simply called a borrowing; but in English discussions of Lojban, the Lojban word fu'ivla is used. This is probably because in Lojban, unlike Loglan, a certain set of CV templates is reserved for borrowed words.
In the new phonology for Lojban, the consonant q and the vowel w were removed, and the consonant h was replaced by x. The consonant ' (apostrophe) was added with the value of [h] in the International Phonetic Alphabet, but its distribution is such that it can appear only intervocally, and in discussions of the morphology and phonotactics, it is described not as a proper consonant, but a "voiceless glide". (This phoneme is realized as [θ] by some speakers.) A rigid phonotactical system was made for Lojban, but Loglan does not seem to have had such a system.

Loglan
Lojsk was conceived by Ari Reyes, heavily influenced by Loglan, Lojban, Universal Networking Language (UNL), Esperanto, Visual Basic, Dutton's Speedwords, Ceqli and Guaspi. It is designed to be more single-syllable oriented. If possible, that would nonetheless lead Lojsk to be even more sensitive to noisy environments than Lojban is, therefore its practicability in oral communication may be questioned.

Lojsk
Voksigid by Bruce R. Gilson attempts to construct a predicate language of a different type from those which had gone before. Its syntax was somewhat influenced by Japanese, and its vocabulary was based mostly on European language roots. Loglan and Lojban both uses word order to mark the various places in the predication, but because remembering which position means which role in the predication might be beyond easy memorization for most people, Voksigid was designed in order to overcome this issue.

Voksigid
Guaspi is a descendent of Lojban and Loglan which uses Chinese-like tones to mark grammatical structure, develop by Jim Carter. By using tones instead of structure words, and cutting predicates from two to one syllable, Carter has fixed a minor flaw in Guaspi's predecessors -- they take a lot of syllables to say things.

Guaspi
Q: How many Lojbanists does it take to change a broken light bulb? A: Two: one to decide what to change it into, and one to figure out what kind of bulb emits broken light.
This joke makes use of two features of the language; first, the language attempts to eliminate polysemy; that is, having a phrase with more than one meaning. So while the English word "change" can mean "to transform into a different state", or "to replace", or even "small-denomination currency", Lojban has different words for each. In particular, the use of a brivla such as the word for "change" ("binxo") implies that all of its predicate places exist, so there must be something for it to change into. Another feature of the language is that it has no grammatical ambiguities that appear in English phrases like "big dog house", which can mean either a big house for dogs or a house of big dogs. In Lojban, unless you clearly specify otherwise with cmavo, such modifiers always group left-to-right, so "big dog house" is a house of big dogs, and a "broken light bulb" is a bulb that emits broken light (you can achieve the desired meaning with the appropriate cmavo or by creating a new word, in effect saying "broken lightbulb").

Lojban is the first language in the world that used the Roman alphabet without mandatory capitalization of letters in formal writing; in fact, such capitalization is discouraged..
The Lojban logo is defined as a Cartesian coordinate system superimposed on a Venn diagram, as the result of a poll of the members of the LLG. This definition does not mention color, but it is traditionally reproduced with the coordinate system in red and the Venn diagram in blue. No official explanation of its symbolism exists, but one might reasonably suppose that each of its components stands for the language's two major characteristics: the coordinate system for "rationality" (analytical observation and representation of groups of things), and the Venn diagram for "universality" (all of the possible logical relationships between groups of things). For more details and alternate proposals, see Lojban Logo.
The official LLG book The Complete Lojban Language is often referred to as The Big Red Book due to its appearance, or simply The Book.
Beginners of Lojban often misproduce expressions in the language as they conceive of things from their own peculiar cultural point of view. For those idiomatic, biased Lojban expressions there are common terms, the English version of which is malglico (mabla + glico), meaning "damn English".
Something of the flavor of Lojban (and Loglan) can be imparted by this lightbulb joke:
Lojban project started exactly 100 years after Esperanto was created (1887-1987). Trivia

Notes

Goertzel, Ben: Potential Computational Linguistics Resources for Lojban. Self-published, March 6, 2005. [2]
Speer, Rob; Havasi, Catherine: Meeting the Computer Halfway: Language Processing in the Artificial Language Lojban. Massachusetts Institute of Technology, 2004. [3]
Lojban vs Loglan comparison
Lojban with attitude!. Lojban for Beginners. Retrieved on 29 June 2005. General/Miscellaneous

lo cunso selpeisku
le karni be fi la camgusmis by Robin Lee Powell
C.I.T.O.K.A.T.E. by Matt Arnold (direct link to his Lojbanic contents) Personal blogs

Learning courses/resources

coirodo (a course featuring a children's book)
Conversational Lojban
Lojban: A Logical Language by Robin Turner
What is Lojban? by John Cowan and Nick Nicholas
Lojban For Beginners by Robin Turner and Nick Nicholas
Everyday Lojban by Lojban.org
Lojban Introductory Lessons
jboski: an online Lojban-to-English translator by LLG
Parallel 2: a free program for parallel reading and listening, based on the implicit learning approach
jMemorize:
Popup.app: a GNUstep based vocabulary learning tool that can use cmafi'e to extract the vocabulary from a given text.
Quizlet:
Lojbanic Number Trainer: a simple web tool
Software Assisted Learning: miscellaneous software listed on Lojban.org Beginner

gimste: a full list of Lojban gismu
Diagrammed Summary of Lojban Grammar Forms with Example Sentences by LLG
The Lojban Reference Grammar by John Cowan
The Level 0 Booklet
Using UML to understand Lojban
jbovlaste: an official Lojban dictionary project Literature

xirli'u selsanga: a poem by Federico Garca Lorca, translated by xorxes
skanunydji: by Michael Helsem
sipna pemci: by Arnt Richard Johansen