I want to DL one. Is there any available for Linux platforms and more important, is there any free CADs for it?

Ah, nevermind!
I just dl'ed QCad and EAGLE.

But now for 3D CAD programz????

K3DCad is a 3D CAD program for KDE2 (Linux) to design black-and-white-depthmaps and 3D stereograms (a la "Magic Eye").

The goal of GNU CAD is to create a professional, but open-source CAD (Computer Aided Design) Package for linux/unix systems. The system will eventually include a plugin interface as well as scripting capability, possibly through pearl,bash or other language.

http://sourceforge.net/projects/gnocad/]GnoCAD is a Solid Modeler for Linux. It use OpenCASCADE libraries and Gtk+/GNOME. The purpouse of this project is to give to Linux community a functional and useful CAD system.

Don't know if any of these are good, just checked sourceforge.

You might wanne try Blender

try the link below:

http://www.tldp.org/HOWTO/Commercial-HOWTO.html

Can you use Blender as CAD? I didn't know that - but then, I don't use Blender too much either