I've been following the threads about CAD by Bronxilogically Violated,
and have been too apathetic to mention:

If you want to make 2D _drawings_, the kind of stuff that you actually
give to machinists to make parts*, then QCad is pretty good. It's a
marketing vehicle for some "full version" 2D cad system that you have to
pay $$ for, but QCad itself is open source and pretty darn good**.

I use it for drawing model airplane plans, mostly, and it works just fine.

* Well, all but the most complicated parts, in which case everyone gives
up on the whole 2D drawing thing and the shop just asks for your 3D model.

** Except splines suck -- one of their sales points for the commercial
product, when translated from Sales to Pithy, reads "and splines don't
suck".

--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com