I use this one:
http://www.uib.no/People/hnohf/
It is called: Ardalambion. Some very nice stuff on there and some of it very in depth 🙂
There is a book that goes over ALL the Languages of middle earth and teaches how to read and write most of them. It's a bit of a small and Hard book to find but well worth getting it. It's called "The Languages of Tolkien's Middle-Earth." And if you go to Google.com and Type in Download Sindarin Dictionary, you might find a good elvish dictionary.
The book sounds cool, and I might get it, because I'm having trouble with my sources. You'd be suprised at the things my Sindarin Dictionary doesn't have. Thus I concur: Where can we find it? I agree also about the http://www.uib.no/People/hnohf/ being a good source for the languages on Middle-Earth. I am currently learning Adunaic, Sindarin, and Black Speech. Sindarin is definitely the hardest, as it was the most advanced. So, if you please, could you post about this book? I can't wait to get it, now.