Wikimapia.org Volunteer edited online satellite mapping
Wikimapia - Let's describe the whole world!
Wikimapia is a Web 2.0 project inspired by Google Maps and Wikipedia, and it could be described as a combination and of the two. The site and project were created by Alexandre Koriakine and Evgeniy Saveliev.
From a large world satellite style world map you can choose from many cities and zoom in to place you know and add their location/outline and description or name to the growing Wikimapia map.
You can read and learn more at Matt Jones' blog.
(Note that Wikimapia.com redirects to Wikimapia.org.)