CAD - Design 2D or 3D objects, computer aided design software:
Check here for "free" design software.
Related to CAD are Drawing programs that work on meshs:
Rhino, Maya, Meshmix, Blender
CAM: This a general classification of software used translate designs into information the mill or printer can understand. Different machines need different CAM:
Roland MDX: Custom Roland software installed on computers at Makeit Labs imports DXF, STL, BMP
Plasma CNC: Custom software installed on computers at Makeit Lab, imports DXF files
Repetier host is also useful, even though we don't presently use it on any machines.
Viewers, DRC(design rule check), and assisting tools.
http://circuitpeople.com/ This is a great sanity checker for viewing PCB gerber files before routing or ordering