Blender - Blender is the open source, cross platform suite of tools for 3D creation.
Slic3r - STL-to-GCODE translator for RepRap printers Here comes Slic3r! Its features are: - speed
Sculptris - Sculptris: Enter a world of digital art without barriers.
Repetier - Software for controlling RepRap style 3D-printer like Mendel, Darwin or Prusa mendel.
ZBrush - ZBrush is a digital sculpting and painting software solution.
MatterControl - MatterControl is a free, open source app that lets you organize and manage your 3D prints.