Morpholio Trace - Morpholio Trace is widely called to be the dream software of the designers and architect.
A360 VIEWER - Free online CAD Viewer
Qlone - 3D scan any object with your iPhone or iPad
STP Viewer - Free STP Viewer - free software that lets you view 3D STEP files (.stp, .step file format).
DWG FastView - DWG FastView for Windows is a lightweight dwg/dxf drawing viewer and editor produced by Gstarsoft, no need of dwg format conversion, vector graph magnified without distortion and full compatible with AutoCAD DWG/DXF.
Glovius - Extensible & customizable 3D viewer, for consumption of product design data.