Unrestricted freeware, Windows XP / Vista / 7 / 7 64 bit / 8 / 8 64 bit. Not allwed to use for commersial purposes It aslo hase a huge library, called 3D Warehouse, where users and manufactures contribute with millions of ready to use 3D objects. It is even better that about generic CAD software such as AutoCAD and Microstation.
You can use it for 2D and 3D designs and has amazing capabilities. SketchUp Make is the most widespread free general use CAD software.