Autodesk AutoCAD - Autodesk AutoCAD is a commercial computer-aided design (CAD) and drafting software application.
FreeCAD - An open-source parametric 3D modeler
SketchUp - 3D for Everyone
Redeye Apps - A common data environment to collect, manage and share engineering information
LibreCAD - An open source 2D CAD application for Windows, Apple and Linux.
nanoCAD - nanoCAD is a pro-grade 2D CAD system with native DWG support and full customizability.