Double-Tongued Word Wrester
- A growing dictionary of words from the fringes of English, including jargon, slang, and loan words.
- http://www.doubletongued.org/

Urban Dictionary
- U.S. slang dictionary whose submissions and various definitions are subject to votes for inclusion.
- http://www.urbandictionary.com/

SlangSite.com
- A dictionary of slang, webspeak, made up words, and colloquialisms. Submissions welcome.
- http://www.slangsite.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

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

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

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

The Online Slang Dictionary
- A global dictionary of English slang.
- http://www.ocf.berkeley.edu/~wrader/slang/

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

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

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

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

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/