Just received my Pi today!
I had seen Widdershins case ( http://www.thepixelpump.com/widdershins ... i-case.php ) in this forum & used it as a guide.
I was lucky to find a rear projector TV around the corner that was being tossed out. It has a Fresnel type lens made of a poly carbonate. So I snapped & grabbed some. I went through about 3 attempt before it came out OK.
It is translucent, but if you get in the sweet spot it magnifies the awesomeness of the Pi; a true sweet spot.
Total cost: ~$3.50. I had to buy some brass nuts & bolts & may get some brass washers too. But that's for later.