http://geoguessr.com/?
This is really cool, but beware! Huge time suck ahead! It "plops" you down somewhere in the world and you have to wander around to get some clue as to where you are. You can zoom in on the itty bitty world map in the corner to get more accurate.
It's really funny what you use for clues-language, foliage, water bodies, what side of the road cars are driving on. Even if the signage is in English, subtle wording changes make a difference. I guessed "England" correctly (at least somewhere in the right country) because of a sign marked "car park", which we don't see in America. However, when I've been wrong, I really blow it!