RE
Yeah it looks weird, but its a high density (high R value) foam used for home insulation.You can get it up to 4 inches thick.
Its lite weight and pretty strong. Plus you can shape it easily, and if you cover it with foam safe epoxy and it becomes like fiberglass. It works really well if you want to make very strong 3D shaped (robot) parts.
I use a different brand of this stuff to coat it http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXPT46&P=0