GRASS GIS ON MAC OS X

http://wwwamb.bologna.enea.it/forgrass/

"GRASS GIS (Geographic Resources Analysis Support System) is an open source, Free Software Geographical Information System (GIS) with raster, topological vector, image processing, and graphics production functionality that operates on various platforms through a graphical user interface and shell in X-Windows. It is released under GNU General Public License ( GPL )."