While increasingly online facilities are being offered to view GIS datasets, these are generally limited in their ability to do complex analysis. Thus desktop software remains an imperative for serious work.
Quantum GIS is free software which is cross-platform - Mac, Windows and Linux. It is an excellent choice we highly recommend.
URL: http://www.esri.com/ ESRI software is the most widespread software used for GIS research and analysis in the Academy. It is however expensive and complex.
URL: http://www.pbinsight.com/welcome/mapinfo/ MapInfo is a standard GIS application that provides sophisticated tools for GIS research and analysis. It is much more affordable and supplements ArcGIS (above) nicely for some functions.