For all you people want to to learn to model 3D stuff on your computador:
You can now download Bryce 5.0 for free. Apparently bug ridden, and hence a ploy to encourage people to upgrade, I figure hey, its a way to learn, cant be all that bad.
Linky:
http://www.daz3d.com/program/bryce/bryce5free.php?trid=446713850 Mac link is on the same page.