Some might know it already but Google's "version" of a geo-wikipedia, a sophisticated online application for user-generated geographic data is now launched! http://mapmaker.google.com/ To see an example of what could be achieved fast, zoom in (using the Mapmaker page and NOT the public http://maps.google.com pages, they are not the same data!) to Western Africa, or Kenya, India etc. where data shows, and check out some large cities to see the detail already captured.
Mainly about New York and Countries of the World. Variety of information and tips