Social Explorer

Social Explorer is dedicated to providing demographic information in an easily understood format, data maps. We serve hundreds of interactive data maps of United States.
Here, you can visually analyze and understand the demography of the U.S., explore your neighborhood and learn about the people that live around you.

This is amazingly addictive. I just popped in to take a look and relized I had been looking for an hour. Above is a map showing education percentages for the U.S below High School level for 2000. They have all sorts of stuff. Race, income, education, population (and more) all the way back to 1910 an zoomable down the the census zone level. Very cool.