For those that don't know about TheFunTheory.com "This site is dedicated to the thought that something as simple as fun is the easiest way to change people’s behaviour for the better. Be it for yourself, for the environment, or for something entirely different, the only thing that matters is that it’s change for the better." Here's another "fun" idea to promote change, the Scratch Mat. This will definitely get your friends to wipe their feet off when they come to your house.
Finally, here's the Bottle Arcade. I grew up in Michigan where we have a $.10 deposit on all bottles, giving us somewhat of an incentive to recycle. This is a great idea though, would definitely get kids into recycling and makes it MUCH less monotonous for everyone else