Carleton County Colloquialisms  
   Dictionary of the colloquial language of Carleton County, New Brunswick, Canada and Aroostook County, Maine, USA. Audio clips accompany each entry.
   http://dooryard.ca/

A Dictionary of Slang  
   English slang and colloquialisms currently used in the UK.
   http://www.peevish.co.uk/slang/

London Slang  
   Online word and phrase dictionary of Cockney rhyming slang. Also includes examples of film slang.
   http://www.londonslang.com/

PseudoDictionary  
   Covers slang, made up words, "webspeak", colloquialisms and accepts contributions for new entries.
   http://www.pseudodictionary.com/

Slang Search  
   Definitions of common words in English-language slang, organized by subject area.
   http://www.slangsearch.com/

The Online Slang Dictionary  
   A global dictionary of English slang.
   http://www.OCF.Berkeley.EDU/~wrader/slang/

Sayings Explained  
   Searchable database of well-known sayings, phrases, and slang, along with definitions and origins.
   http://brochuresonline.net/sayings/

Insultmonger.com  
   An alphabetized compendium of expressions considered offensive, vituperative, and insulting.
   http://www.insultmonger.com/slang/index.htm

The New American Sub-Standard Politically Incorrect Dictionary  
   A glossary of offensive terms or terms with offensive meanings.
   http://www.americansubstandard.com/

Businessballs.com - Cockney Rhyming Slang  
   Origins, derivations and dictionary translations. Cockney rhyming slang uses substitute words, usually two, as a coded alternative for another word.
   http://www.businessballs.com/cockney.htm