Netfabb - Innovative software solutions for 3D printing and additive manufacturing.
OpenSTL - A GUI-based STL (stereolithography) file viewer and editor
Free View Expert - Entry level tool targeted for viewing, verifying, dimensioning and communicating 3D geometry...
STLView - A Free STL Viewer for Android and Windows
ADA STL Viewer - FREE software for visualisation of STL or OBJ meshes
Tatlin - Multi-platform Gcode and STL viewer for 3D printing