of 16, 20
Open Street Map Mumbai Mapping Party
Open Street Map creates and provides free geographic data to anyone who wants them. Sometimes they'll throw "mapping parties," where people get together and coordinate walks around cities with GPS devices, generating reliable maps and resulting in movies like these. This one showes people running around Mumbai, starting off in the outer districts and eventually meeting up to map the more central areas of town.
The project is run by volunteers, and it's in its early stages right now, but as GPS devides become more prevelant and access to the data that people generate starts to open up more, the data starts to get alot more granular, and it's easy to see how this kind of activity could become the de-facto way that cities are mapped moving forward.
For example...