Within Agent Lambda's large office all the walls (except for the one with console) are covered by bookcases full of leather-bound volumes, dog-eared paperbacks, student notebooks with tea spilled on them, papyruses, parchment manuscripts, and other pieces of writing.  There are literary works, scientific studies, humorous writings, and all possible writings by Elves, about Elves, or even remotely concerned with the Elves.

Lambda sees you enter, opens her sleepy eyes and shows you around the place...

Elven Languages in Tolkien Fanfics: Which one should I use?
This is a rather long, detailed essay that briefly touches the history of Elven languages, and discusses what language should be used for which kind of Elves during which time period.  Problems and limitations I have come across are also addressed.  If you have any questions, or feel I have missed something, or if you find a mistake (Errare humanum est!  I am only a human, and not burdened by a degree in linguistics), e-mail me.

"You know why I am called Agent Lambda? No?  You see, Lambda comes from Quenya word 'lambengolmë', which means, roughly, "a linguist." Someone who studies languages. Oh yes, dear, it is "languages."  Exactly that.  Do you know how many there are?  One?  No, who has a better answer?  Three?  Nope.  You see, there are Quenya and Sindarin, but there are also Avarin, and Telerin, and Nandorin.  And not to be forgotten are such dialects as Doriathrin, or old forms like Old Sindarin, Noldorin, Ilkorin, or Pra-Eldarin.  Read this note, it will help you grasp the idea of who should be speaking what language, dear, it will save PPC agents a lot of time.  And you, I see you already know what language your character should be speaking, you just want a good dictionary.  Of course I have a couple just for you."

The best site on Elven languages.  It has short history and word lists for all major and minor Elven languages, and most other languages Tolkien has created.  An excellent Quenya course is also on this site.
The Elvish Linguistic Fellowship
Another excellent resource.  This site has the complete analysis of the Middle-earth languages used in the movies, and a ton of articles and resources.  This is intended for serious Elvish learners.  Explore this site, and you will find something of interest, whether you are an expert in Sindarin consonant mutations and can conjugate a noun through all the Quenya cases, or if your Elvish is pretty much limited to the word "Mellon."

Take extra notice of all the wonderful links they have on these two sites.  Just follow the links, and I don't doubt you will find everything you are looking for, and many things you didn't even know you were looking for.  If you have any questions, I will be happy to help you in any way I can.  Just send me a note in English, Russian, or German at tar_daedin@hotmail.com or crazyhellga@yahoo.com.