FairData 2000 - interactive political maps
A series of interactive maps originally created for non-profits and political organizations. Details voter registration, election results in 2000 and 2004, and census data. There are also voter registration and turnout pdf files for all Minnesota towns above 15,000 population.
The link above is for Minnesota, although other states are represented on the site as well. While the map itself isn't from a government source, all of the data seems to be cited from various government agencies.