FreeCAD: Your own 3D parametric modeler
www.freecadweb.orgAccessible, flexible & integrated FreeCAD is a multiplatfom (Windows, Mac and Linux), highly customizable and extensible software. It reads and writes to many open file formats such as STEP, IGES, STL, SVG, DXF, OBJ, IFC, DAE and many others, making it possible to seamlessly integrate it into your workflow. Designed for your needs
Free Cad Viewer
free-cad-viewer.aliscience.orgViewer is a handy and free CAD viewer software for Windows, Mac, or mobile phones. With the help of this freeware, you can view designs or drawings made by any CAD tool. If you have historical 2D design drawings created in retired CAD systems, it will help you view and measure these old designs for either design reuse, servicing, or
Free online CAD Viewer. View AutoCAD DWG/DXF, HPGL ...
https://sharecad.orgFree online 2D and 3D CAD viewer. It supports AutoCAD DWG/DXF, STEP, STP, IGES, IGS, STL, SAT (ACIS®), Parasolid (x_t, x_b), SolidWorks ™ (sldprt), PLT, ...