I can't see my house from here: WiFiMaps has interactive map of wardriving database: Although nodedb has been around for quite a while, offering geographic information system (GIS) mapping of access points to graphical maps, WiFiMaps has a crisper display and shows the results of wardriving and other sources. It's a good way to tell whether anyone knows your network exists (mine hasn't been stumbled in this database), and to find out how active Wi-Fi is in your neighborhood or community.
A colleague wrote in after I posted this to remind me of the fine folks at wigle.net who have 900,000 access points in their wardriving database along with downloadable Java and Windows client software which lets you load browsable map modules; you can also browse certain cities through a Web interface. While the maps aren't as pretty, they're quite good, and the URLs correspond to specific locations where WiFiMaps hides the URL-to-location mapping. They don't show my home network either (thankfully?).