The Michelangelo exhibit at the British Museum is fantastic.
Given his known crankiness and paranoia he usually destroyed his
prepatory drawings. Somehow the ones that were in his
estate (didn't manage to get rid of them before he died I
guess) were dispersed and yet many have been brought
together for the first time in centuries.
Included is one of his studies for Adam - the most famous panel of the Sistein Chapel - the creation of man.
If you're not going to visit my fav web zine has an article and some images.
http://www.iatwm.com/200604/Michelangelo/michelangelo.htm