Urban Outfitters weighs in with a woven rug made from recycled bike tires. It only comes in black, of course, but it's a decent size (3'x5') and completely affordable ($28).
This stunning circular floor mat by Inghua Ting (and available at Branch) is made entirely from vintage leather belts! It's rather small (27.5" diameter) and pretty pricey ($648) but it'll certainly get noticed.
For the shag lovers out there, Gaiam introduces the Reclaimed T-Shirt Spaghetti Rug. The large (5'x7') and heavy (40 lbs.) rug is hand-hooked and made from unused t-shirt factory remnants. Unused, in this case, is good because we wouldn't want to have to think about walking around on someone else's pit stains! Good links: • Potholder Rug • Recycled Plastic Doormat • Sources for Cool Indoor/Outdoor Rugs