Google Image Labeler: Google is somewhat brilliant. Finally giving into the fact that they can’t determine the meaning of everything, they’ve created a game to help them identify what’s in images.
You and a faceless, anonymous partner start. An image comes up, and you start typing labels for it. Your partner is doing the same thing. You can see how many labels he/she has entered, but not what they are. When you both type the same label, you get some points and a new image. There’s a “leaderboard” — some people have hundreds of thousands of points.
So, Google let’s you play a game, and, at the same time, gets two people to review their images, help identify what’s inside them, and incidentally check each other’s work.
Insanely, wickedly brilliant.