I’ve never seen The Mathematics Genealogy Project until just now. It’s pretty incredible, covering the professional history of almost 100,000 mathematicians. I did some searches on the math PhDs I know and they were all there. The math greats are there and they even offer posters of anyone’s entire genealogy.
I love magnificent obsessions like this one — that someone went to the trouble to create it and that they keep it up to date (one math geek I know just finished summer 2005 and he was there), eventually creating this IMDB.com of math.