WiGLE - Wireless Geographic Logging Engine
WiGLE provides a place for wardrivers to post wireless SSIDs that they detect while they are out driving.
We consolidate location and information of wireless networks world-wide to a central database, and have user-friendly java, windows, and web applications that can map, query and update the database via the web.
Then it takes these access points and plots them on a searchable map for all to see. It looks like they are color-coding the APs based on their security settings, although I have not found a legend for the colors on the map.
You can also download various clients applications and load maps into them, making it easy to see where the closest WiFi is and whether it is open or not.
An alternative objective of the site is to raise awareness of unsecured wireless networks.
Overall, WiGLE aims to show people about wireless in a more-technical capacity then your average static map or newspaper article.