Dictionary between Tolkien and English Translation Online
These wordlists (I should not call them "dictionaries", which would be something more ambitious) are available as RTF files: Quenya-English, English-Quenya and Quenya Reverse Wordlist.
Dictionary of the Elvish Language.
The Sindarin dictionary project.
A Taste of Elvish
Tolkien once stated that he had "tasted" a number of languages rather than studied them (MC:192).
Ardalambion Of the Tongues of Arda, the invented world of J.R.R. Tolkien.
Elvish to English Dictionary.
Tolkien Glossary of Rami Rekola
Glossary of Tolkien's ‘The Lord of the Rings’ (English - Finnish).
English to Elvish Dictionary.
Dictionary of the Elvish Language