Lefteh, you’re usually spot on with your answers, so I hope you won’t be offended when I tell you that you’re way off in this case.
The beautiful geometric sans-serif font that is used in the images and headings on the Obama website is actually Gotham. There’s been a little stir in the design community about it over the course of the campaign, because it really is a lovely, very tasteful font and demonstrates a much better handle on design than any political campaign in recent memory. Gotham comes from Hoefler & Frere-Jones, one of the best contemporary type foundries.
I’m not sure immediately what the serif is—perhaps after I do a little research, I can find it for you. It’s true that the serif in the text headlines is Georgia (a good font to use when designing websites because most every computer has it) the font used in the graphics (buttons, etc.) certainly is not. It’s much too high contrast to be Georgia. I’ll see if I can’t track down what it actually is.