OpenStreetMap

OpenStreetMap is a free editable map of the whole world. It is made by people from the entire world.
People make the maps using data from a GPS device and pictures from airplaces. Map vector information can be downloaded under the Open Database License, and the map pictures can be downloaded under the Creative Commons Share-Alike license.
OpenStreetMap allows you to view, edit and use geographical data in a collaborative way from anywhere on Earth.