CNN has launched a political market website that’s pretty fun to use. Find a market (like “Who will win the Democratic nomination”), and you can buy shares using fake money. They ask a few simple questions that help you narrow down how many shares to buy, and then you can buy or sell based on how the market is doing. Prediction markets like these can be amazingly accurate.
Bonus, the site lets you use an OpenID instead of a password when you create your account, so you can just use your LiveJournal, Vox, AIM, etc. URL and use that password instead of having to create and remember a new one.