I was snooping around the net and came here:

http://www.shapemagic.com/index.htm

In the Freeware section I found:

Shape Magic (it requires Quick Time, for the Hyperstudio it uses). For object creation, it sounds like modelling with a mechano set (but I only skimmed the surface).

Road Maker, for terrains.

In the Download section, there is more content for download, like a pair of earings for Posette.

Thanks for your head up Amish.
Seems to be interesting for some kind of "Extended primitives"
I'd give it a try, but QuickTime is NoGo for me
It's an old program, and at first glance other free modelers seem more powerful (Blender, Wings, and even Anim8or...)
But maybe I'm wrong...

I'm not so keen on putting on QT, myself just for this, but I think the Road Maker does without the Hyperstudio. I shall need to re-read and make sure before I install it.

There are better modellers out there, as you say.