Conlang Directory: In Actual Use

Dutton Speedwords
This language's claim to fame is that it is intended to be a shorthand system as well as a method of international communication. The most common words are the shortest; all are between one and three letters. There is also a short dictionary online. [Dutton][archivist: Richard Kennaway]
The most famous constructed language. It's more regular than evolved languages, easier to learn, and based on vocabulary taken from several European languages. It has probably a million or so speakers, and there are even a few native speakers. See also Don Harlow's Esperanto site in North America, and Martin Weichert's Virtuala Esperanto-Biblioteko in Sweden.
Intented for international communication. Glosa takes its roots from Greek and Latin and it's word order from English. It's mostly uninflected; you can use the same word as a verb, noun, or adjective. What inflections it does have are marked with dashes so they're easy to pick out. Some critics say it's just a code for English. There are a few more articles about it here, some of which are in Esperanto.
Invented for Star Trek by Marc Okrand, the language is particularly interesting (to me anyway; it's OVS and very agglutinative) and alphabet. Cool, eh? You can get fonts for Mac and Windows. [Marc Okrand]
Invented by Suzette Haden Elgin, Láadan reverses some of the gender biases English has. Its vocabulary contains a lot of interesting words which are very hard to explain in English. This and the loglans (TLI Loglan, Lojban, -gua!spi) are probably the best ones to learn if you're interested in experimenting with the Sapir-Whorf hypothesis (the idea that language affects thought, in one way or another) [Suzette Haden Elgin]
Invented by James Cooke Brown. An attempt to fuse the rigor of formal logic with the expressiveness and flexibility of natural language. It's syntactically unambiguous and machine parseable. [James Cooke Brown]
A descendent of Loglan. There was a schism relating to arguments about ownership and copyright.
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