My son put me on to this. He is an advanced AutoCAD and Solidworks user. Solidworks is an advanced 3d drawing system. The same people are making available, a 2d cad drawing system capable of creating and handling DWG drawings. I am not a CAD user as such but my son says this appears to be a very robust program. The best part is the price - FREE. You can get it here:
http://www.draftsight.com/