A nice CAM software that will fit most of your desktop prototyping needs.
Scale, Mirror and Rotate the geometry
Set a bottom level (the minimum Z-value to be machined).
Define and select cutters
Distance between the parallel toolpaths, and stepsize along the toolpath
Speeds: feedrate and spindle speed
Roughing options: skin thickness and layer height
Simple 2D machining
Bitmap machining (grey-value to Z-Height conversion)