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.
LibreCAD - An open source 2D CAD application for Windows, Apple and Linux.
LiteCAD - Create, edit, view, and print 2D CAD drawings using the file formats: dxf, dwg, shp ;Download-Size...
DraftSight - Discover Dassault Systèmes®' DRAFTSIGHT™ Professional CAD software that lets you create, edit, view and markup any kind of 2D drawing. Learn more here.
ZWCAD Viewer - Cross-Platform .DWG | .DXF | .DWT R12-2013 Viewer