So GrabCAD is not a CAD package in its own right?!
After signing up I thought I can start designing but realize that the cooperation is only about uploaded files nots and ???.
Also GrabCAD is expanding it's services: toolbox Toolbox will be an ever evolving web based CAD modeler.
I'm a big fan of collaboration too, and for me, it happens here everyday with some awesome results with clients and fellow GrabCAD'rs.
Some examples of good times on GrabCAD
Fish Aquarium - 38 Models, 100+ renderings, one download!
mōna mission project - GrabCAD on the moon
Jurassic City - Before CAD walked the Earth
GrabCAD ~ POD Races
You're in the right spot!