OneLook Dictionaries provides links to over 550 general and specialized dictionary.
A web of On-Line Dictionaries From Afrikaans to Yiddish, this site has links to more then 800 dicitiaries in 160 languages
Merrian-Webster Online Perhaps the best on line dictionary and thesaurus according to the stinking article in USA Weekend where i found these dictionarys
Travlang's Translating Dictionaries Translates words between more then a dozen languages. Coolest feature: sound clips of basic words in each language
The New Galactic Phrasebook Trekkies can get up to warp speed with this Klingon dictionary