A360 VIEWER - Free online CAD Viewer
STP Viewer - Free STP Viewer - free software that lets you view 3D STEP files (.stp, .step file format).
Glovius - Extensible & customizable 3D viewer, for consumption of product design data.
VariCAD Viewer - 3d cad,mechanical cad,mechanical engineering,linux cad
PartXplore - The most powerful, high-speed?CAD file viewer and analyzer
IDA-STEP v4 - Iges2step is a free and elegant CAD viewer application for Windows.