Digital History

http://www.digitalhistory.uh.edu/maps/maps.cfm

Amazing collection of historic maps

National Geographics Xpeditions

http://www.nationalgeographic.com/xpeditions/atlas/

Hundreds of printable maps

The World Factbook

http://www.odci.gov/cia/publications/factbook/docs/refmaps.html

From the CIA: hundreds of maps, up to date

Library of Congress Map Collection

http://memory.loc.gov/ammem/gmdhtml/gmdhome.html

Download maps: most not protected by copywrite