Cockney sample
from Gillian Lane Plescia's
Cockney for Actors,
available from Dialectresources.com
Cockney Features: mp3 pdf
The breakdown of the features of Cockney are outlined one lexical set at a time, which you can follow along with in the pdf.
Samples of Rhyming Slang:
Discussing Cockney Rhyming Slang (see the wikipedia article on Rhyming Slang)
Discussing the "Bengazy"
Discussing a "Brahma"
Discussing the term "Crowns"
Discussing being "knackered"
Discussing "plimsoles"
Discussing terms for ugly
Famous Cockneys:
David Beckham
Gary Oldman
Boxer Nigel Benn
Singer Billy Bragg
IDEA Samples:
The London section of IDEA doesn't feature many strong "Cockney" accents. Afterall, many Londoners aren't working class! However, England 42 isn't bad, and is the one I would use over all the others.
Other Cockney resources:
GenAm, Stage Standard, RP, & Cockney Breakdown/Comparison
RP, Estuary English & Cockney Comparison