When I lost my wallet and was prowling the shops for a replacement, I wasn't impressed with what was available. Time to make something! This is the nicest wallet I have ever owned. It's very quick to use, and designed to be as small as possible. So it's not bulky in your pocket. It includes two card slits, a coin pocket and another pocket for more cards and notes.
Construction is from a single piece of inner tube, with staples instead of sewing. It's very simple and quick to make (and cheap, obviously!). The wallet in the pictures below is actually my second attempt. See this instructable if you're interested in making one
Update: I've used this wallet for a year or two now and it's still holding up pretty well. A couple of the staples have broken, but they're easy to replace. A word of warning: I left mine lying in the sun and it warped a few of my cards. They still work luckily!
Update: 6 years now and still going strong.