If you like Buddhabrot, a friend of mine used MapReduce to create a high-res image of Buddhabrot's cousin: Nebulabrot. Kinda fun.

How it was done: http://scienceblogs.com/goodmath/2008/01/databases_are_hamme...

Images: http://www.danvk.org/wp/2007-04-06/nebulabrot/