Predict wallstreet stock exchange:
http://www.predictwallstreet.com/
Do you think that stock will go higher or lower at the close of the markets tomorrow?
Predict the technologies people will be searching the web for in the future:
http://buzz.research.yahoo.com/
Put your (fantasy) money where your mouth is by buying stock in the technologies you believe will be popular and selling stock in the technologies you think will flop.
Predict the news:
http://us.newsfutures.com/
Buy, sell, trade predictions of tomorrow's news.
Cars:
http://www.edmunds.com/insideline/csx.html
Think you know which vehicle will be the next big thing? Put your instincts to the test with CSX—Car Stock Exchange—a prediction market game that lets you buy and sell virtual car stocks alongside other enthusiasts from around the world. Build your portfolio just for fun…or compete against your peers for monthly prizes.
Predict future political events:
http://www.thewsx.com/
Welcome to the Washington Stock Exchange, a market for predicting future political events like the next President, whether the Democratic Party will control the US House (HOUSE06), or whether the US will launch military strikes on Iran (IRANWAR)...
http://njpse.nationaljournal.com/
NJPSE is a free fantasy political stock market. NJPSE players predict specific political outcomes.
Predict the media:
http://mediapredict.com/
And even blogs!:
http://blogshares.com/index.php
BlogShares is a fantasy stock market for weblogs. Players get to invest a fictional $500, and blogs are valued by incoming links