DWGFREE - DWGFREE is an online platform that comes with a comprehensive collection of CAD blocks that can be downloaded without the need for registration.
FreeCAD - An open-source parametric 3D modeler
CADMAPPER - Instant CAD files for any location on earth
LibreCAD - An open source 2D CAD application for Windows, Apple and Linux.
Cadbull - Cadbull is a website that comes with an advanced collection of CAD blocks and DWG design, facilitating architects and designers to get done with their projects efficiently.
SketchUp - 3D for Everyone