One thing we've learned this election is that averaging polling data gets you pretty close to an accurate prediction. But particular polls are often badly off. According to Fordham's Costas Panagopoulos, some of the least accurate polls came from surprising sources. Gallup, Rasmussen and NPR were among the worst, whereas YouGov, PPP and Ipsos/Reuters all nailed it:

Source: Costas Panagopoulos, John Sides

RAND also had a good night. Their poll, which used an innovative methodology that tracked 3,500 people through Web surveys, predicted that Obama would get 51.7 percent of the two-party vote. He got 51.1 percent. Getting it right to within 0.6 percentage points is pretty good.