Refer to There are lots of free gis software listed in the website:
http://www.freegis.org/
http://www.freegis.org/database/viewobj?obj=1116 FreeGIS-summary on Quantum GIS
Name: Quantum GIS (QGIS): cross platform free software
Homepage: http://qgis.org/
How to install?
http://www2.qgis.org/en/site/forusers/alldownloads.html