For the fifth anniversary of the Google Maps API I helped Google create a Google Maps mashup that allows map developers to pin their Google Maps mashups to a map. The idea was to highlight some of the amazing maps that people have created with the API all over the world.
The map is hosted on Google App Engine and uses Google Fusion Tables to store users' submissions. To help other map developers create their own user submitted maps for Google App Engine the source code for the map has now been added to Google Project Hosting:
Mappybirthday on Google Code
Mappybirthday itself now has nearly 600 maps listed and is becoming a reasonable resource to find local maps. For example, if you zoom into San Francisco, you can find a Google Map that will help you find somewhere to rent, a map that lets you view real-time ship positions in the Bay, a real-time map of NextBus buses, and a map of crime in San Francisco.
Of course if you add a map to Mappybirthday you might also find your map is reviewed on Google Maps Mania!