Check out 50 States in 10 Minutes. There are a couple of links to the game in the post; I think the last update has the easiest interface. I did pretty well, getting the first 48 in just over 2 minutes and then agonizing over the two I stupidly forgot (Illinois and Minnesota, duh) for another couple of minutes.
When you’re done with that, try your luck with 192 Countries in 10 Minutes. That one was quite tough, especially since spelling counts and some of the countries are listed by their full name (e.g. The Bahamas). I still managed to get about 110 on my first try, and my second try was much better, getting around 150 and then just running out of time.
How did you do on those? If you’re feeling guilty about how many you missed, the site World Geography Quizzes has a bunch of games designed to help you learn countries, capitals, bodies of water, state and province names, and more.