All mentioned are great - but expensive. Check TurboCad - I haven't used it, but it looks good for the money and has been around for a while. Check this one - $129.00. It's usually at your local large computer stores. It won't export easily to CNC, but you didn't say that was needed.

[link]http://www.turbocad.com/TurboCAD/TurboCAD15/TurboCADDeluxe15/tabid/702/Default.aspx[/link]

might try this for fun - again just found it today, haven't tried it.
[link]http://sketchup.google.com/[/link]

Solidworks and A/D Inventor are basically the same, but Rhino is aimed at more complex items, like cars, telephones, things that are completely rounded in my experience.

If you are a CAD student, you can also get a good student price on the big names mentioned.

Stay with the 3D progs - don't get Autosketch or AutoCad or programs that just draw a line drawing - you can generate those drawings from the 3d program quickly.

Dennis