A Dictionary of Slang
A searchable dictionary of over 3000 English slang terms and colloquialisms currently used in the UK, including links, word articles and a select bibliography.
http://www.peevish.co.uk/slang

Cockney Rhyming Slang
The 'largest' online collection of London's best loved language. A searchable A-Z resource that accepts submissions.
http://www.cockneyrhymingslang.co.uk

Cockney Rhyming Slang Game
an aid which helps one to make sense of Cockney.
http://www.amherstlodge.com/games/cockney/cockney_index.htm

London Slang
A site dedicated to the slang of London, sometimes called 'Estuary English', including many examples of Cockney rhyming slang, a 'just heard' page and related film/books.
http://www.londonslang.com

Merseytalk
Beginning with an introduction, Merseytalk provides an alphabetical and categorised listing of the rich language coined and used in Liverpool and the wider area of Merseyside.
http://www.louisville.edu/~tavan001/Merseytalk.html