Autorealm

Available

 * Original project page: http://autorealm.sourceforge.net/
 * Open source development now at https://bitbucket.org/bmorel/autorealm

Description
AutoRealm - A Mapping Tool is a CAD-based mapping application intended for use by role playing games developers. However, it can easily be used for mapping the real world.

Autorealm is a free and open source analogue to the more sophisticated, but commercial, Campaign Cartographer.