Think you know your geography? Like learning about the world?
Here are a few fun games for those who like geography. marzipanni just reminded me of a really popular google maps mashup that is making the rounds, you may have played it.
http://geoguessr.com/
You are placed at a random Google street view location and your task is to guess where you are in the world. You can move up and down the road to gain clues. I got 12,900 for my first try, but I was lucky to be placed in quite a few places with some clues.
For those into more classical geography here's Globetrotter XL. See how close you can get to the right location based on city name and country, you are under a timer too:
http://www.kongregate.com/games/crafics/globetrotter-xl
And if you want to limit yourself to just countries there this one:
http://www.purposegames.com/game/97318ad7
A few years back I made a game of this and learned every country in the world and all their capital names (except a few small island nations I was about 95% for 190 or so countries). As well I taught myself every US state and the order of every US president and was working on the Periodic Table of Elements. But I've lost most of this now since I haven't practiced in a long time. It's really fun to see how much you can memorize though.