Summary

I took one of my wife's Julep boxes (it was the smallest one lying around the house) and turned it into a case for my Raspberry Pi.

The pi is mounted to 3/16" hardwood plywood using brass risers and computer screws that I had lying around.

Instructions

Materials
-Cardboard Box that will fit the Pi, with internal dimensions of ~2" high
-Wood mounting material (I used 3/16" hardwood plywood because it was the best fit in my shop)
-Brass risers from a computer case or motherboard kit.
-Computer bolts that fit into the risers (the thicker threaded ones)

Executive Summary of Instructions

Cut wood so it fits in box
Arrange Pi on wood
Transfer mounting holes to wood
Drill through wood with 7/64" drill bit
Screw bolts into risers
Screw risers into holes in wood using a screwdriver. Remove screws from risers
Place Pi on risers, screw computer screws into mounting holes and risers
Use small drill bit and drill to guess at the center locations of I/O ports (don't hit the Pi!)
Use big drill bit to gouge out more material
Unfold box and clean up all your crappy looking drill holes with a box cutter, refold box.
Optional - Cut out hole in top, print out pi grill, and glue on the top for ventilation.

Full instructions are in a PDF in the thing files.

Pi case out of a Cardboard Box