Criteria:
- The dictionary should be bilingual. (I've made a similar thread for monolingual dictionaries.)
- List a single site you think is best, not a list of different sites and not a link to such a list. You should be able to search for a word directly from the site you link to. (It's probably the link you're most likely to use yourself if you want to look up a word online.)
- If someone else has already added your language and you think a different site is better, add that one too!
- Keep my list in your message and your own to it (so ideally by the end of the thread we'll have a long list in one post).
WordReference English/Spanish with other language pairs available (searches 2 dictionaries, thesaurus, forum, conjugations)
Keeleveeb English/Estonian with other language pairs available (searches 100+ dictionaries/databases/corpora simultaneously)
Саамские словари Russian/Kildin (four dictionaries but you have to search them individually, small phrasebook)
Līvõkīel-ēstikīel-lețkīel sõnārōntõz Livonian/Estonian/Latvian (dictionary with sentence examples, conjugations)
Vadja keele sõnaraamat Estonian/Votic (dictionary with sentence examples & dialect variation)
Thai-Language.com English/Thai (dictionary, bulk lookup, phonemic transcription, forum, a bit of grammar)