Get your geek on
I've suddenly become obsessed with geography. If you were a fan of "Where in the World is Carmen Sandiego" back in your youth (or still, I won't judge) you might want to help out your country (and state, if you're in the US) in the Geography Challenge. You can play up to three times a day without registering (although registration is free if you feel like it) and your score gets added in to everyone else who plays from your country and state. If you need a refresher (like I did--I swear there are more countries today than there were back in fourth grade), you might want to try the more forgiving quizzes at this site or this one.