Quantum GIS, an easy-to-use, free, open-source mapping program that is similar to ArcView 3.2
www.qgis.org/
GeoDa, a spatial statistics program with powerful spatial econometrics tools, developed by Luc Anselin geodacenter.asu.edu/
National Historical GIS, at the Univ. of Minnesota. High quality shapefiles/boundary files for use with programs like ArcView, ArcGIS or Quantum GIS
www.nhgis.org/