If you care at all for the environment, you're probably taking 2 minute showers, using recycled paper, and drive a hybrid car, which leaves plenty of water, paper, and fuel for those of us who are too lazy to care. But for you, the environmentally conscious bunch, we present the Sinkpositive. It's a sink on top of a toilet, which uses the tank (is that what it's called?) water for hand washing before using it again for poop flushing.
Of course, we only recommend this for married people, since most non-hippy women would probably bolt when seeing this mounted on your toilet. On the other hand, imagine how much fun it would be to pee into the top and bottom and see urine be used to flush urine.