Stanford has compiled a map of the 2008 presidential vote that shows voting at the precinct level. The map is interactive and really shows the rural-republican and urban-democratic leanings.
from Stanford.edu Each dot represents a precinct, but as you zoom in, you will notice differences in the sizes of the dots, with larger dots corresponding to more votes. Precincts in which Obama received more than 50 percent of the vote are colored blue, and precincts with McCain majorities are colored red. In order to illuminate the marginal precincts, we have outlined the dots in white for precincts where the winner’s margin of victory was less than 5 percent. The white dots only begin to appear as you zoom in on a state or region.