Blender - Blender is the open source, cross platform suite of tools for 3D creation.
Cura - Cura aims to be a end solution for personal 3D printing with RepRap based machines.
FreeCAD - An open-source parametric 3D modeler
Slic3r - STL-to-GCODE translator for RepRap printers Here comes Slic3r! Its features are: - speed
MATLAB - A high-level language and interactive environment for numerical computation, visualization, and programming
Repetier - Software for controlling RepRap style 3D-printer like Mendel, Darwin or Prusa mendel.