A360 VIEWER - Free online CAD Viewer
STP Viewer - Free STP Viewer - free software that lets you view 3D STEP files (.stp, .step file format).
3D Viewer Online - 3D Viewer Online is a web service and works on computers, tablets and smartphones.
Glovius - Extensible & customizable 3D viewer, for consumption of product design data.
Autodesk DWG TrueView - Get a free DWG viewer to view, open, edit, and convert .dwg files, the native file format for AutoCAD files. DWG Trueview includes DWG TrueConvert.
JT2Go - The no-charge viewer for 3D JT data