NSGS (U.S. Geological Survey)
http://www.usgs.gov/education
Great information for teachers. Elementary and middle school teachers will want to see the lessons on maps. They have lessons for all major grades levels.

Geography @About.com
http://geography.about.com/
About.com has volunteer specialists who collect resources in their area of study. This is a good place to look for resources.

All the World's Maps
http://www.embassyworld.com/maps/maps.html
Maps of most countries.
Perry-Castañeda Map Collection
http://www.lib.utexas.edu/maps/historical/index.html

Maps from Eduplace
http://www.eduplace.com/ss/maps/
Over 60 outline maps for classroom use. Maps include: World, Africa, Asia, Europe, South and North America, United States, Historical, and Primary outline maps.
You do have the right to copy these for classroom use. "These maps may be printed and copied for personal or classroom use." Is posted on this Houghton Mifflin Company web site.
You will need Acrobat Reader to view the maps which is available at www.adobe.com

National Atlas of Maps - "Reliable geographic information that covers North America. We have begun by collaboratively building "frameworks," the essential map layers that provide a foundation for all other maps."

The Historical Atlas of the Twentieth Century
http://users.erols.com/mwhite28/20centry.htm

United Nations' Cartographic Section
http://www.un.org/Depts/Cartographic/english/

American Memory Map Collections
http://memory.loc.gov/ammem/gmdhtml/gmdhome.html

Places in the News
http://memory.loc.gov/ammem/gmdhtml/plnews.html

The National Atlas
http://nationalatlas.gov/

National Geographic’s Map Machine
http://plasma.nationalgeographic.com/mapmachine/

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

TopoZone
http://www.topozone.com/