Atlapedia Online
Lots of maps as well as accompanying statistical data.
http://www.atlapedia.com

Color Land form Atlas of the United States
http://fermi.jhuapl.edu/states/states.html

Cultural Maps
http://xroads.virginia.edu/~MAP/map_hp.html

Earth and Moon Viewer
View Earth from the sun, the moon or from any of a host of satellites in orbit. Day and night regions can be displayed or turned off. Also shows real-time weather conditions around the globe.
http://www.fourmilab.ch/earthview/vplanet.html

Green Map System
Maps designed to help locate eco-friendly information and businesses, from museums to grocers to renewable resources. These "green" community maps trace human impact on cities from San Francisco to Utrecht, Holland. Visit Kids' Neighborhood for maps built by youngsters
http://www.greenmap.com/home/home.html

Library of Congress: Map Collections 1544-1996
More than 4.5 million old and new maps.
http://lcweb2.loc.gov/ammem/gmdhtml

Microsoft Expedia Maps
Type in a geographic name or point of interest to get a map There are links to local news and weather, also information on the city from the Encarta Encyclopedia.
http://www.expediamaps.com

National Atlas Of The United States
Shockwave plug is needed. You will find animated, interactive maps or create and download custom map layers without a charge..
http://www.nationalatlas.gov

National Geographic.Com
Site contains political and physical maps of the continents to "The Heavens." In the online version of that famous star chart, images from the Hubbell Telescope may also be found
http://www.nationalgeographic.com

Perrt Castaneda Library Map Collection
http://www.lib.utexas.edu/Libs/PCL/Map_collection/Map_collection.html

Rare Map Collection (American Civil War)
http://scarlett.libs.uga.edu/darchive/hargrett/maps/civil.html

Rare Map Collection (Colonial America)
http://www.libs.uga.edu/darchive/hargrett/maps/colamer.htm

Rare Map Collection (Revolutionary War)
http://scarlett.libs.uga.edu/darchive/hargrett/maps/revamer.html

The Library of Congress Country Studies
http://lcweb2.loc.gov/frd/csquery.html

Tiger Mapping Service
U.S. Census Bureau, site where you can download maps with titles like 1990 Population Distribution in the United States.
http://tiger.census.gov/

Yahooligan?s Maps
http://yahooligans.yahoo.com/reference/factbook/maps/a.html