GRASS GIS. at <http://grass.osgeo.org/>

gvSIG. at <http://www.gvsig.org/web/>

MassGIS. at <http://www.mass.gov/anf/research-and-tech/it-serv-and-support/application-serv/office-of-geographic-information-massgis/>

NASA WorldWind. at <http://worldwind.arc.nasa.gov/>

OpenJUMP. at <http://www.openjump.org/>

PostGIS. at <http://postgis.refractions.net/>

Quantum GIS. at <http://qgis.org/>