GRASS GIS Windows, Mac, Linux
By The GRASS Development Team
For Everybody

this is a Geographic Information System (GIS) used for geospatial data management and analysis, image processing, graphics/maps production, spatial modeling, and visualization. GRASS is currently used in academic and commercial settings around the world, as well as by many governmental agencies and environmental consulting companies.

For additional information, please refer to: GRASS: LSU Overview.

Quantum GIS Windows, Mac, Linux
Quantum GIS
By Quantum GIS
For Everybody

Quantum GIS is an open source GIS (Geographic Information System) application that runs on Mac, Windows, and Linux. It’s sort of a professional grade version of Google Earth, allowing you to work with detailed maps in raster, vector, or database format. It also opens files in the format produced by Arc GIS.