Wardriving
Software links:
PC/router:
EarthStumbler (converts NetStumbler files to KML for Google Earth)
Mobile:
WiFiFoFum (Windows Mobile) (Files can be natively saved as NS1, XML, KML, and more)
MiniStumbler (Windows CE)
Websites:
Wireless related File Extensions and related tools
Check out a Google Map of a few spots I've captured on my HTC Touch Pro
A quick map of some data I capture in my apt complex
(Produced via Google Static Maps API)