Rmap is a project mainly written in RUBY and JAVASCRIPT, it's free.
Radical Cartography (with Google Maps API)
Oberlin College Oberlin, OH 41.294728 -82.220144 We went there
A radical cartography project. A community-built overlay of Google Maps to help people get involved in radical projects in their area.
Idea by that rascal, Kalan Sherrard.