I just stumbled across this open-source GIS suite while reading a journal paper.
"Commonly referred to as GRASS, this is a Geographic Information System (GIS) used for geospatial data management and analysis, image processing, graphics/maps production, spatial modeling, and visualization. GRASS is currently used in academic and commercial settings around the world, as well as by many governmental agencies and environmental consulting companies. GRASS is official project of the Open Source Geospatial Foundation."
I just installed it and am excited to play around with it once I have some free time. Install on a windows machine requires Cygwin, but was a breeze. There are also install packages for MacOS and a bunch of Unix-based OS (such as Ubuntu).