My post a little while ago about a cheap book light inspired me to see how cheaply I could make an ereader case, and it turns out I can make one out of stuff in the recycle bin. You're looking at one of my neighbor's magazines and a rubber band.
Most magazines are too big for the average ereader, so you'll need to fold the magazine around the gadget. I have my Kindle pulled out of the case so you can get a better mental image of how to do it.
I was going to do a case made from duct tape, but I got stuck halfway through.