Any other sites like TradeSports and WSEX?

[threei]

Are there any other sites like these two? Are they the two largest? I checked them out after reading about them here last week, when people were talking about trading AI contestants.

[threei]

bump

[Duckstabber]

Betfair (http://www.betfair.com) is by far the largest betting exchange in the world. No yanks allowed though...