GRASS GIS Complete on Mac OS X - Complete installation package for the GRASS GIS (Geographic Resources Analysis Support System) for Mac OS X. Requires Mac OS X 10.2.8 and later with last security update and X11. - http://wwwamb.bologna.enea.it/forgrass/index.htm
MacGimp - Port of the open source Gimp graphic software to Mac OS X (requires X Windows). Includes news, surveys, and links. - http://www.macgimp.org/
POV-Ray - The Persistence of Vision Raytracer. - http://www.povray.org/