Also, they correctly predicted Obama winning within something like 3-10 points or something, in 2008.
For the 2008 Presidential Election, FiveThirtyEight.com also used computer models to simulate the election 10,000 times per day in order to provide a continually up-to-date assessment of probability for electoral outcomes. The method proved to be highly accurate, as Silver correctly predicted the winner of 49 of the 50 states in the presidential election, as well as every Senate race in 2008.
Checking out that site it doesn't look the same as it used to so I don't know.
EDIT: He partnered with NYTimes so I don't know if he still does what he used to do.