The Atlas provides many different types of maps, including shaded relief, satellite image and historical maps that date back to the 1800s. The maps are comprehensive and intelligible, with state boundaries clearly marked.
http://fermi.jhuapl.edu/states/states.html
Created by the United States Department of the Interior. "Unlike the big bound map collection of 1970, the latest National Atlas includes electronic maps and services that are delivered online. We are using information presentation, access, and delivery technologies that didn't exist 30 years ago to bring you a dynamic and interactive atlas. But we have held fast to our tradition of producing the finest maps in the world. We think nationalatlas.gov™ is more useful than any bound collection of paper maps.”
http://nationalatlas.gov/
Select a region and country. Click "go"; a page opens with links to a map and other information. Part of the lonely planet web site.
http://www.lonelyplanet.com.au/dest/
Nearly 600 National Geographic maps at your fingertips. Crisp and clear, these page-size maps were designed for printing and copying.
http://www.nationalgeographic.com/xpeditions/atlas/index.html
Part of the NationalGeographic.com website.
http://plasma.nationalgeographic.com/mapmachine/index.html
Maps and geography of every country, state, and continent. Part of the About.com web site.
http://geography.about.com/library/maps/blindex.htm
This world atlas includes every continent, country, dependency, island, province, state and territory on the planet!
http://www.graphicmaps.com/aatlas/world.htm
Military maps. Environmental maps. Maps that "record the evolution" of American cities. This Library of Congress site is rich in content and easy to use, offering more than 4.5 million old and new maps. Want something as obscure as a bird's-eye view of Marshalltown, Iowa, from 1868? It's here. Search by keyword or browse the sections. Once you find the map you need, you can zoom in or out, adjust window size and then download it for later viewing.
http://lcweb2.loc.gov/ammem/gmdhtml/
The mother of cartography sites on the Web, the PCL seems to have every map imaginable, from a chart of the Azores dated 1845 to a street map of Central Baghdad circa 1998.
http://www.lib.utexas.edu/maps/index.html
A page of links to street and road map web sites.