Open Street Map is "an editable map of the whole world, which is being built largely from scratch using GPS traces, and released with an open content license." The map is created primarily from gps data posted by users who do field surveys in their areas and use wiki-style collaborative software to create the map. Yahoo! aerial imagery is also a source the project uses to derive mapping data.

Anyone can browse the map and export data, including image formats and vector data. To get started, there is a Beginner's Guide as well as a frequently asked questions page (FAQ).

A related source of geospatial data is the Public Geospatial Data Project. If you're looking for free gis data, the Public Geospatial Data Project is a valuable clearinghouse. The project's goals include:

• Promote the use of open geospatial formats

• Promote public access to state-collected geodata

• Run a repository of open geodata

• Present and explain licenses for public geodata