LibreCAD - An open source 2D CAD application for Windows, Apple and Linux.
KediCAD - CAD/CAM/ FEA software for Linux
SketchUp - 3D for Everyone
DualCAD - Freeware cad application that handles the basic needs of most Microstation users
FreeCAD - An open-source parametric 3D modeler
High Design - HighDesign software is for architectural design, engineering, MEP, detailing, and construction.