Google Maps hacks!
Someone finally did a WiGLE and Google maps mashup!
http://wigle.rustyredwagon.com/
The same guy did this greasemonkey script for googlemaps to enable even more overlays (Topo, Terra, Urban) the Urban one is awesome and has a much better zoom than any of the others.
http://www.dasnet.org/node/101
Theres even more here:
http://www.gnik.com/wiki/GoogleMaps