LibreCAD - An open source 2D CAD application for Windows, Apple and Linux.
Morpholio Trace - Morpholio Trace is widely called to be the dream software of the designers and architect.
SketchUp - 3D for Everyone
Qlone - 3D scan any object with your iPhone or iPad
FreeCAD - An open-source parametric 3D modeler
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.