South London Bookswaps [updated]
The Book Swaps for London blog argues that “When it comes to Station book swapping, it really is all about South London“.
There are book swaps at Wimbledon, Raynes Park and (reportedly) Morden stations. You can find out more about the Wimbledon Station bookswap here.
The Book Swaps for London blog aims to support book swaps in “200 of the near 700 underground and rail stations in Greater London” in time for the Olympics.
Update: BookMachine interviews London Book Swap (Jan 2012).