Dave Leip runs the Atlas of Presidential Elections. This site is impressively detailed, with maps of every U.S. presidential election, broken down by state, and within states, by counties. Perusing the older elections, it is clear that ragged outcomes are more the norm than we've come to expect. And there are plenty of interesting factoids to dig up. For example, how many electoral votes did Ronald Reagan get in 1976? (No, that's not a typo).
Dave also maintains a blog on the site where he chases down electoral details (will Maine finally split its electoral votes?, how would past elections have turned out if we all had used Colorado's proposed electoral split method?). Fascinating stuff.