Intrade enables one to 'bet' on political events. For example, you can bet .85/share that Ron Paul will be the Republican nominee. The price is up 3% today.

You can bet against this occurrance by selling shares, and yes, you can do short sales.
Here's the complete explanation of how Intrade works:
http://www.intrade.com/v4/misc/howItWorks/theBasics.jsp
Too cool for school!