Human Computation

There are several cases where humans excel computers at computation. This is harnessed in Luis von Ahn's work on Human computation.

http://video.google.com/videoplay?docid=-8246463980976635143

If you want to see a demo, you can see here: http://images.google.com/imagelabeler/

I now see that some other implementation of the same thing, which is much more interesting and pragmatic:
http://bmaurer.blogspot.com/2007/05/recaptcha-new-way-to-fight-spam.html

Interesting indeed.