A360 VIEWER - Free online CAD Viewer
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.
STP Viewer - Free STP Viewer - free software that lets you view 3D STEP files (.stp, .step file format).
Autodesk Design Review - Design Review lets you view, mark up, print, and track changes to 2D and 3D files.
Glovius - Extensible & customizable 3D viewer, for consumption of product design data.
ZWCAD Viewer - Cross-Platform .DWG | .DXF | .DWT R12-2013 Viewer