Teaching people to type with video games.
This is an excellent example of how you take a mundane task and turn it into a game. Typing skills are crucial to anyone who uses a computer. The people at phoboslab.org have a neat little game reminiscent of Asteroids, except that you must words on your keyboard to fire your lasers. Sure it seems like a game when you play it, and it is! However, every time you play, you are really practicing your typing skills.
http://www.phoboslab.org/ztype/
http://www.phoboslab.org/ztype/