Disclaimer:  the links listed here are some of the ones I have used in my research for my stories or future stories. <wink>   One last note, I don't know the politics nor beliefs (not entirely anyway) of any of these sites, so as in anything:  Caveat Indagatrix (loose Latin translation:  searcher beware). <G>

Languages:

American Slang Commonly-Used American Slang	Australian Slang Larry's Aussie Slang and Phrase Dictionary
Buffy Slang Buffy Slanguage	Civil War Slang Civil War Slang
College Slang The College Slang Page	Drug Slang Slang Drug Terms
English Slang The British Slang Dictionary	General Slang Slang and Language Links
Irish Slang Some Irish slang	London Slang London Slang
Mountain bike slang The Dictionary of Mountain Bike Slang	New Zealand Slang Kiwi Speak Kiwi - Words & Phrases
Prisoner Slang A Prisoner's Dictionary	Roadie Slang Dictionary of Roadie Slang
Russian Slang The Alternative Russian Dictionary	SCA Slang The Dictionary of SCA Slang
Scottish Slang Scottish Slang Productions

Online Translation:

General translations Language Dictionaries and Translators Latin and Italian Translations Promt Reverso Online Thesaurus Your Dictionary.com