I just answered a reference question about President Bush's middle name. In the process I found this website and thought I'd share:
Genealogy of the presidents of the USA
Users click a president's picture and then click on names in family tree charts. FYI, (in case you forgot), George H.W. Bush's maternal grandfather's name was George Herbert Walker.
Of course, a list of presidents is available <http://memory.loc.gov/learn/orientation/preslist.html> within the "people" pathfinder <http://memory.loc.gov/learn/orientation/people.html> on the Learning Page <http://memory.loc.gov/learn/>.
Also, lots of good web links about Presidents are available via the Internet Public Library's POTUS: Presidents of the United States feature: <http://www.ipl.org/ref/POTUS/>.