Another Google feature I stumbled upon while I was searching for images .
How does it work?
Google image labeler allows you to label images to help improve the quality of Google's image search results.
When playing, you will be randomly paired with a partner who is also playing at the same time. Within 2 minutes, you will both be shown the same images and you will type keywords you associate with that image. You will receive points when the keyword or label you assign, matches the label provided by your partner. The number of points will depend on how specific your label is. After you match labels, you will be shown another image until the time runs out.
It's like a game (you don't even have to be signed in to play).