MatterControl - MatterControl is a free, open source app that lets you organize and manage your 3D prints.
Cura - Cura aims to be a end solution for personal 3D printing with RepRap based machines.
Slic3r - STL-to-GCODE translator for RepRap printers Here comes Slic3r! Its features are: - speed
Repetier - Software for controlling RepRap style 3D-printer like Mendel, Darwin or Prusa mendel.
Blender - Blender is the open source, cross platform suite of tools for 3D creation.
OctoPrint - OctoPrint is the snappy web interface for your 3D printer that allows you to control and monitor all aspects of your printer and print jobs, right from your browser.