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
SketchUp - 3D for Everyone
Simplify3D - Professional 3D printing software streamlines the process of 3D printing, leading to better results.
LibreCAD - An open source 2D CAD application for Windows, Apple and Linux.