If you are looking for a printable map of the United States (or several actually), for one genealogy project or another (perhaps tracking migration, where everybody is living now, etc.), then look no further than NationalAtlas.gov – The maps are in several different formats/sizes, and there are even individual state maps.
A compliment to these is the Perry-Castaneda Library Map Collection at the University of Texas, that I’ve mentioned before, that covers historical maps. The PCL collection has a large range of maps covering various periods of history (not just the US, but the world as well).