http://www.yourdictionary.com/diction1.html#multi
Dictionaries in many languages, and also many disciplines. This is THE site for finding dictionaries and thesauri online. There are also some obscure dicitionaries You never know when you might need:
1,000,000 Scrabble Links (huge 320K HTML file)
The Cliché Finder
Dictionary of Difficult Words (12,700 words in all fields)
A Little Etymology
A Glossary of Place Names of Indian Origin in Florida
Measurement Converters
Read the Bible in 55 Different Languages
Short Word Lists (the Words for 1-10) in 300+ Native American Languages
Spell Web See how popular your spelling is on the Web
Yak-Yak On-line Danish-English-Norwegian-Swedish Word Finder (Spellchecker)
but for other languages, these are good online dictionaries, including:
DICTSEARCH All-in-one Dictionary Search: Bulgarian, Catalan, Czech, Danish, Dutch, English, Estonian, Finnish, French, German, Hungarian, Indonesian, Italian, Norwegian, Portuguese, Russian, Slovene, Spanish, Swedish, and Turkish which translate from 69 source languages into 73 target languages.