Cura - Cura aims to be a end solution for personal 3D printing with RepRap based machines.
OpenSTL - A GUI-based STL (stereolithography) file viewer and editor
MatterControl - MatterControl is a free, open source app that lets you organize and manage your 3D prints.
STLView - A Free STL Viewer for Android and Windows
Slic3r - STL-to-GCODE translator for RepRap printers Here comes Slic3r! Its features are: - speed
Free View Expert - Entry level tool targeted for viewing, verifying, dimensioning and communicating 3D geometry...