FreeCAD - An open-source parametric 3D modeler
Blender - Blender is the open source, cross platform suite of tools for 3D creation.
SolidWorks - Dassault Systèmes SolidWorks Corp. develops and markets 3D CAD design software, analysis software, and product data management software. SolidWorks is the leading supplier of 3D CAD product design engineering software.
MatterControl - MatterControl is a free, open source app that lets you organize and manage your 3D prints.
LibreCAD - An open source 2D CAD application for Windows, Apple and Linux.
Onshape - Onshape is the first full-cloud 3D CAD system. It runs in a web browser and on any mobile device.