Using rainwater to water your plants is a nice "why not?" idea which has been around forever and is starting to be done again. Depending on how much space you have, you can do this in a big way by harvesting rainwater with rain barrels or in a not-so-big way with a rain catcher. These plastic rain catchers sit outside, making a spot in your garden a little more interesting with their colorful sculptural shape. After a rainfall, use the collected water (3 quart capacity) for some of your plants instead of turning on the hose. Available at Chiasso for $48.