SketchUp - 3D for Everyone
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.
Autodesk AutoCAD - Autodesk AutoCAD is a commercial computer-aided design (CAD) and drafting software application.
Autodesk Design Review - Design Review lets you view, mark up, print, and track changes to 2D and 3D files.
Assetforge - Asset Forge allows anyone to create 3D models and 2D sprites using building blocks.
ZWCAD Viewer - Cross-Platform .DWG | .DXF | .DWT R12-2013 Viewer