I keep telling myself not to send these notes to the list because they aren't written in Croquet/Squeak, but I keep coming up with better external modeling packages. Here's one now!
Flux Studio at
http://www.mediamachines.com/fluxstudiofeatures.html is a polygon modeler for X3D and VRML content, with other import/export options too. Free-during-beta and open source, it includes modeling and animation. Nice.