A very simple STL that is actually a simplification of the STEP-file by Marco Alici (http://marcoalici.wordpress.com/2012/01/28/me-and-the-raspberrypi/#)

I simplified it so RepRaps/Skeinforge etc don't choke on it. Please don't use this as a reference to make cases. I didn't double check the geometry. Don't come crying if your injection moulding-mould doesn't fit the Pi we're all waiting for.

Print for reference. Think of the printed model as a teleported version of your preordered Pi. Profit.
Prints nicely on an Ultimaker (some overhanging parts)