allwords.com
"A dictionary with all definitions in English, but the ability to search for a word in English, French, German, Dutch, Italian, and Spanish. Additionally, there is pronunciation file for each English word."

Babel Fish
Translate anything. The site also features "Systran Personal" (which will "translate your documents in seconds).

Bin's On-Line Dictionary
Search various on-line dictionaries.

Chinese Character Genealogy: An Etymological Chinese-English
"This web site and its associated printed dictionary present a series of zipu or 'character genealogies' which show graphically the close interconnections between over 4,000 characters according to the Shuowen Jiezi and subsequent research by traditional etymologists."

English-Estonian Dictionary
Here's a searchable index that translates a word in English to its Estonian equivalent, and vice versa.

Foreign Languages for Travellers
Find translations of travel words and phrases, numbers, shopping and dining, directions, places, times and dates. The site also has sound files to help with pronunciation.

foreignword.com
"Foreignword.com has created a site that centralises the access to on-line dictionaries and glossaries, gives an overview of the latest translation software products, allows exchange of knowledge among translators and offers web-space to interested translators. The more theoretical issues of linguistic technology also have a special place in foreignword.com."

FreeTranslation.com
FreeTranslation.com is an easy-to-use site for rapid translations where you can get the "gist" of foreign language text and Web pages.

Japanese-English Dictionary Portal
"The Japanese-English Dictionary Portal provides easy look-ups of entries in Jim Breen's Japanese-English dictionary, WWWJDIC. By highlighting characters, words, or phrases on a Web page in Kanji/Kana, Romaji, or English, and then clicking on the JEDP menu, you can automatically find those characters or words in the dictionary. "

The Alternative Dictionaries
"This is an experimental 'internet collaborative project', which means that all entries are made by internet users. There are now dictionaries for English, Dutch, German, Portuguese, Spanish, Catalan, French, Italian, Polish, Russian, Esperanto and several other languages."