A great application for Android is WarDrive. It records the GPS location of wireless networks it sees and exports the data as KML which can be viewed in Google Earth.
That's part of my bus ride home.
If you zoom in there's almost a 1:1 ratio of homes to networks.
Green dots are open networks, yellow are WEP and red are WPA2. I love some of the names, there's lots of Netgear and linksys but a few funny ones like "baby killer".
Aside from exporting to KML, Wardrive can upload to Wigle which is a fun site if lacking in internationalisation.