Mozilla Labs have released a plug-in for FireFox called Geode that helps websites work out users' locations. The service uses Skyhook’s Loki technology to map the Wifi signals in your area to your location. Similar to Yahoo's Fire Eagle, Geode users can decide what level of location information they want to reveal to a website, 'exact location', 'neighbourhood', 'city' or 'nothing'.
This service should be of interest to many Google Maps developers. Using Geode it is possible to present a map to users centred on their current location and provides an alternative to Google's own google.loader.ClientLocation function.
Using Geode websites are able to offer up location specific information. So, for example, a music site would be able to automatically work out a user's location and deliver a list of gigs in that town. Fire Eagle and Pownce have already added Geode functionality to their sites.
There is also a demo Food Finder site using Geode to show cafes and restaurants within walking distance of your current location. However, to prove that this is an 'experimental add-on', Food Finder currently won't work for me (no wi-fi signals?) and I just get this rather attractive error message .
Looking at the html of the page I can tell you that Food Finder uses Yelp to load 'coffee', 'tea' and 'cafe' venues around your current location on Google Maps.
Soren Johannessen has produced a test tool to compare Google's geocoder with Geode. Soren says that Geode is more accurate for his address (I can't test it because Geode still doesn't work for me).
Soren's test tool has Danish instructions but it is pretty intuitive so non-Danish speakers should have no problems. The map at the top will show your position as determined by Geode and the bottom map will show your position using Google's geocoder.