Trade anything, really
"The price is set by TradeSports members who decide the fair (or market) value for the contract. A price of 0 (or close to 0) would indicate a contract/event that is NOT going to occur (according to our members). A price of 100 or close to 100, would indicate that the event IS going to occur."
"E.g. If you bought 100 “Bush to win in ’04” contracts at 57 (57 being $5.70) you would be investing $570 (100 times $5.7) to win $430 (ie. 100 times $10-$5.70)"
If this takes off, it could become an important prognosis tool, as people would be rewarded for predicting the correct outcome. This is pretty much what the Pentagon wanted to do in their Policy Analysis Market, which of course got killed as soon as two ignorant blowhards got wind of it.