Just an FYI: I found
this site a couple days ago but forgot to share it. The site itself is a paid membership site designed to aid cartographers in compiling data and making visuals for them (which some of you might be interested in... I dunno), but it also has a list of clean images for county maps for all US states plus regions and territories. There are PUMS files and some ZIP code maps for counties and cities, as well. It's basically only useful for US elections, but still a great resource.
Miles, you might want to include the link in the OP, if you think that would help.