I have been powering away at full steam in my little workshop. Specifically, I chose to build a rotational casting machine so that I could use my urethane molds to make hollow objects.
The purpose of the machine is to rotate a mold in every direction possible. This is done so that a small amount of casting material within the mold coats the inside of the mold, leaving a thin layer, and making a hollow object.
The machine I built actually worked, so I made an Instructable for it, which is now featured on the homepage of Instructables. Here is the direct link for it too.
As noted in the Instructable, I will not be held responsible for any inadvertent pregnancies, rodent infestations, snow storms, or sightings of James Dean due to the machine's construction.
Here is a video of me using the machine to cast a hollow rhino head.