I use POVRay it can be found here I believe
www.povray.org
With that I use Moray, which is a graphical interface using POVRay... Both are shareware
http://www.stmuc.com/moray/index.html
They aren't huge downloads and well worth it if your interested in 3d modeling... There are other programs out there but since I don't know much about them I'll let others mention them.