Free CAD Software
We only suggest links to help you get going with CAD
Draftsight is made by Dassault Systemes who also make the excellent SolidWorks 3D
Windows and a MAC beta are available.
Worth a look if you are serious about 3D CAD drawing
The Rhino3D link takes you to an excellent 3D program that can be used for 2D. It has a long time limit or none, but limits the saves you can make to 25 and then you can still practice and view.
Rhino3D is also a fantastic viewer that can also measure parts and can load almost anything.
We use Rhino all the time.