After the my cover broke off my Cruzer 512 MB USB drive, I decided to fashion my own case. I saw several ideas floating around on the internet such as cases made of Lego, pez dispensers, and and even a Barbie doll. I cast the USB stick in clear casting resin used to make paperweights out of scorpions or flowers. I picked it up at my local Hobby Store for about $15. It comes it two parts: the resin and the catalyst. If you're making a cast, test it out on some scrap bits and pieces to make sure your ratios are correct.
Check out http://www.tcnj.edu/~jones37/usb.html