My Institute for the Future colleague Mike Love, a philosophy buff who is researching data visulaization, has developed an amazing Wikipedia hack called Geneaology of Influence. He says:
Genealogy of Influence allows you to visually trace the connections between the most influential writers, artists, philosophers, scientists, and mathematicians of Western culture. You can pull up a short bio (stripped from Wikipedia) by hovering over a person's name, or click through to the full Wikipedia article. I also made a colorful hierarchical image of the same data. Link
