Cartographic Images Home Page (historical maps)=>http://www.iag.net/~jsiebold/carto.html
Perry-Castaneda Library Map Collection at UT Austin=>http://www.lib.utexas.edu/Libs/PCL/Map_collection/Map_collection.html
Uchronia Alternate History List (rasfw FAQ)=>http://www.skatecity.com/ah/ 
P.C. Wrede's Worldbuilder Questions=>http://www.io.com/~eighner/wbuild.html