There has been a huge amount of attention on the Google Image Labeler.
Tim O’Reilly has previously described this as bionic software. This relates to humans being required to complete some computational tasks.
In 2003, 9 billion hours were spent playing solitaire. By comparison, it took only 7 million human hours to build the Empire State Building, and only 20 million human hours to build the Panama Canal.
Again, Tim O’Reilly has written up the details of the presentation.
There is also a demo of Peekaboom during the presentation. This is a similar idea but has a reveal feature which allows them to gather more information about which parts of the image more more important.
All these sites/games are great examples of how to encourge humans to collaborate on tasks which are simple ofr humans but complex for computers.