American Panorama (University of Richmond Digital Scholarship Lab)
Atlas of the Historical Geography of the US (University of Richmond)
CaribMap (organization)
Charting North America (New York Public Library) Over 1,000 recently released historical maps.
Classical Atlas Project (University of North Carolina)
Discovery and Exploration (Library of Congress)
Historic USGS Maps of New England and New York (University of New Hampshire)
Historical Maps (eclectic collection of links, many to good online map collections)
Library of Congress Online Map Collection (LC)
Map History/History of Cartography (Website maintained by former map librarian at the British Library)d
Old Maps Online (University of Portsmouth)
Perry-Castaneda Library Map Collection (University of Texas-Austin)
Voting America (University of Richmond)