This forum is dedicated completely to the languages that Tolkien invented for his books about Middle-Earth. Here you have the ability to learn elvish or just ask for help in translation or other linguistic (e.g. phonetical) problems.
The languages of Middle-earth are artificial languages, invented by J. R. R. Tolkien and used in his books about Middle-earth, including The Hobbit, The Lord of the Rings and The Silmarillion. Together with poetry, they are the most important trait of his narrative. In effect, they were Tolkien's instrument in reaching his ultimate goal - the creation of a new mythology for England.
In order to better understand the reasons for this, we should turn to Tolkien himself: in addition to being a gifted student of languages, he also had the ability to feel them. He favored Latin and Greek; he detested French; and he loved Finnish (he described the finding of a Finnish grammar book as "entering a complete wine-cellar filled with bottles of an amazing wine of a kind and flavour never tasted before", Letters, 214).
Language-making had been Tolkien's hobby for much of his conscious life. He is known to have constructed his first languages (Animalic and Nevbosh) at a little over 13; he continued to ponder upon his creations up until his death more than sixty-five years later. This work had always been tightly connected to the mythology that Tolkien was developing, since he believed that a language is incomplete without the story of the people who spoke it - exactly as these people could never be fully realistic if he chose to describe them in English only. One could see in that the reason why Tolkien took the stance of a translator, rather than the original author of his works.
Although Quenya and Sindarin are the most famous and the most mature languages of all those that Tolkien invented for his mythology, they are by no means the only ones. They belong to a whole family of Elvish dialects, that originate in a single Proto-Elvish language. In addition to that, there is a separate (but smaller) language family that is spoken by Men, the most prominent member of which was Westron or the "Common speech" of the heroes of the Lord of the Rings. Several independent languages were drafted as well, for example the Khuzdul language of the Dwarves. The language families are also seen evolving (both because of languages' natural tendency to change and due to borrowing of features from each other).
Some basic links concerning Tolkienian Languages:
Ardalambion Undoubtedly the most important and extensive site about Tolkien's languages (includes a Quenya course). Also take a look at the list of links there.
Mellanoth Daeron The language guild of the Forodrim, the Stockholm Tolkien Society. Information about Tolkien's languages and writing systems including some interesting online publications.
Elvish Linguistic Fellowship The Elvish Linguistic Fellowship (E.L.F.) is an international organization devoted to the scholarly study of the invented languages of J.R.R. Tolkien. The primary activity of the E.L.F. is carried out in the pages of its two journals, Vinyar Tengwar (available by subscription) and Parma Eldalamberon.