Yes, there are a number of free GIS software programs available on the Internet. While some of these are simple GIS viewers with limited or no capabilities, others are feature rich and provide tools for spatial analyses and editing.
Some examples of free GIS programs are:
Windows Only:
• AccuGlobe
• DIVA-GIS
• MapWindow
• TatukGIS
Windows and Mac OS X:
• ArcExplorer
• JUMP
Windows, Mac OS X, and Linux:
• GRASS
• gvSIG
• Quantum GIS
• uDig
For a feature comparison chart of many of the programs listed above, use this PDF created by UNH Cooperative Extension