Stumbled upon this when browsing for HTML5 examples:

http://html5demos.com/geo  (Only HTML5 capable browsers)

If connected to a scanned network.

Links:

http://www.mozilla.com/en-US/firefox/geolocation/

http://en.wikipedia.org/wiki/Geolocation

http://www.w3.org/2008/geolocation/

http://en.wikipedia.org/wiki/Wardriving

Apple Q&A on Location Data

http://www.apple.com/no/pr/library/2011/04/27location_qa.html