AECOsim Building Designer - AECOsim Building Designer is a building design software that allows you to create, analyze and visualize structures of multiple size, form and complexity.
FreeCAD - An open-source parametric 3D modeler
MicroStation - 3D CAD modelling software for architecture and engineering.
SketchUp - 3D for Everyone
midas Gen - Structural Analysis and Design
LibreCAD - An open source 2D CAD application for Windows, Apple and Linux.