There has been a resurgence of the Tolkien books with the release of the three movies in 2001, 2002, 2003. Along with the interest is an interest with learning how to speak Elf (or to be more exact one of the Elvish toungs).

Where is this language documented?

Have a look at this page elvish.org. The first significant pieces of information concerning elvish languages (Quenya, Sindarin, etc.) were published in the Lord of the Rings, appendices E and F to the third volume in particular. Since then, many readers wrote letters to Tolkien, asking for more information, and he answered. Some info was thus published in The Letters of J.R.R. Tolkien.

Then you have the posthumous works (The Silmarillion with a linguistic index by Christopher Tolkien, based on his father's notes, The Unfinished Tales, the twelve volumes of The History of Middle-earth, ...). Most significant is volume 5 from the History of Middle-earth: "The Lost Road and other Writings", which includes The Etymologies, ie. more than fifty pages of elvish roots, and the way they evolved in words in the various elvish tongues (all elvish tongues, and Quenya and Sindarin in particular, are related. All come ultimately from the "Common Elvish"). What's more, most of the names in Tolkien's world have a known meaning.

As for now: Christopher Tolkien (Tolkien's son) sent photocopies of most of his father's papers that are related to the languages of Middle-earth to a group of people who had been editing a fanzine (Vinyar Tengwar) on this topic for several years, with the authorization for them to publish all the material. Thus more and more information is being published concerning Tolkien's languages. "Small" works are published in Vinyar Tengwar, while more comprehensive ones are published in Parma Eldalamberon (most notable are issues 11, 12, 13 and 14. Issue 11 includes the so called "Gnomish Lexicon", Gnomish being an "early version" of Sindarin, and issue 12 the "Qenya Lexicon", Qenya being an "early version" of Quenya, though this is an over-simplification). There are thousands of pages waiting to be published, including detailed grammatical descriptions, etc.

Where is the dictionary, verbs conjugations, grammatical constructs, gender treatments, etc?

The website Ardalambion given in another comment will give you this kind of information, though it represents the view of its author (Helge Fauskanger), which are sometimes subject to controverse. There is a comprehensive Sindarin dictionary compiled by Didier Willis, which you can download on his website Hisweloke (DragonFlame 2.0 is the best way to get the latest version, but it's a Windows program. However, it uses QT and is licensed under the GPL so anyone is welcomed to port it to Unix).

To what degree can complex and subtle nuances be expressed in this one-man made up language?

Tolkien himself wondered how much poetry, etc. an invented language could really reach (see The Monsters and The Critics). But he was of course technically able to build quite complex sentences, with subtle nuances, etc. "one-man language", yet the work of more than half a century (he started devising these tongues in the second decade of the century, and refined them until his death in 1973). However, it's virtually impossible for anyone else to compose a "new" complex elvish sentence, ie a sentence about which one could say "this is true elvish". One reason for that is that Tolkien always changed his mind, his languages were not fixed in any way (though he felt "bound" by the published material). But even if all the published material was "consistent", there would still be huge lacunes in the available knowledge. This may change when more material is published in Vinyar Tengwar / Parma Eldalamberon... But note that most "experts" don't consider "movie-elvish" as genuine. Some even call this neo-Sindarin "mishmash"... -- eldacan

Links

• Resources for Tolkienian Linguistics
• Ardalambion - Site about J.R.R. Tolkien languages
• BBC NEWS - Do you speak Elf?