"OpenStreetMap (OSM) is a collaborative project in the process of building a free, Web-accessible, user-editable map of the world. So far, most of its map data has come through user-contributed GPS traces, but OSM has recently undertaken the bulk import of government-collected data covering the entire United States. The massive import will jump-start OSM's US map coverage, but its sheer size poses an interesting challenge to the project's resources.
"The traditional method of importing data to OSM is outlined on the project's wiki: Individual users collect GPS traces, convert the tracks to OSM form, label any objects, then upload the result to the OSM database. Map images themselves are rendered separately, as needed..."
