They have a new service (game?) that you can use to help them properly keyword random images thay may otherwise lack them in their search engine. Its called Google Image Labeler.Despite the idea that you're doing their work for them, its actually a bit of fun. Though I seem to run into more than a few people who have no idea what a lot of things are or use too simple of words to describe the image, like "man" or "tree". I don't see how those help Google, but I suppose they probably have that figured out.

I find this similar to their idea to release Google SketchUp for free. Why spend the resources to fill Google Earth with 3D models when the internet can do it for you?