Blender - Blender is the open source, cross platform suite of tools for 3D creation.
LibreCAD - An open source 2D CAD application for Windows, Apple and Linux.
AutoCAD MEP - AutoCAD MEP software helps you draft, design, and document building systems.
FreeCAD - An open-source parametric 3D modeler
DataCAD - DataCAD is a computer-aided design and drafting software for 2D and 3D architectural design and drafting
SketchUp - 3D for Everyone