This paper wallet is pretty cool. I usually can't stand papercraft as I don't have the patience to cut out lots of tiny little pieces and try and make paper do things it was never supposed to do, just because I feel empower with non-toxic glue. However, this is dead simple (took me about 10 minutes to make) and pretty useful.

The only problem is that it is wide enough for US dollar bills, but not "real world" money. So right now, I'm using it to store all those store cards I don't want to keep in my main wallet. I'll see if I can fire it up in inkscape later and make it larger. There are some great tips in the comments too. Thanks Lifehacker.