As well as having a distinctive pronunciation and many grammatical features, the language of London is most notable for its Rhyming Slang. This consists of using a phrase that rhymes, sounds the same, as the word you want to say, so 'telephone' becomes 'dog and bone'. Unfortunately, many of the phrases then lose the second word, making it very hard for the outsider to guess the original meaning; 'rabbit' for 'talk' comes from the phrase 'rabbit and pork', but few would be able to guess it.
A lot of the original rhyming slang appeared among the market traders in the east end of London in the 19th century, but it is still used and new words and phrases are being invented all the time. At the moment, it is very fashionable to use famous people's names, so the DJ Pete Tong is used meaning 'wrong'- 'thing's have gone Pete Tong' or Britney Spears is used meaning 'beers'
Apples = apples and pears = stairs ("Get up them apples!")
Barnet = Barnet Fair = hair
Bristols = Bristol Cities = Titties
Bread = bread and honey = money
Loaf = loaf of bread = head
China = china plate = mate ("Alright, me old china!")
Frog = frog and toad = road
Rosie = Rosie Lee = tea ("Fancy a cup of Rosie?")
Butcher's = butcher's hook = look ("Let's have a butcher's!")
Dog and Bone=Telephone
Boat= Boat Race = Face
Septic = Septic Tank = Yank (American) ("He's a septic!" This usage has also given rise to a non-rhyming slang term, 'Listerine' meaning one who is not enthralled with Americans -- because Listerine is "anti-septic"!)
Lionels = Lionel Blairs = Flares - e.g. "Look at those faaking Lionels"
Ruby = Ruby Murray = Curry ("Fancy a ruby?")
Ronan = Ronan Keating= Central Heating
Rub-a-dub-dub = Pub
Nuclear Sub = Pub
Ping Pong = strong
Iron = iron hoof - poof (derogatary slang for a homosexual)
For more examples go here
or to 'translate' English into Cockney Rhyming Slang go here
Please feel free to add any more in the comments section below