I know I'm desperately nerdy for admitting this, but I love a good grey water system. You know, the kind that takes the outflow from your kitchen sink, say, and uses it to water your ornamental landscaping. I've seen (or more likely, read about) some pretty awesome systems that send everything but the toilet water through an elaborate filtration system encompassing gravel beds, aeration fountains, and plants to purify the water enough to use it as irrigation for food crops.
Ours is not nearly so fancy, but it's still pretty keen. Since our laundry outflow was previously uncoupled from the septic system even before we moved in, we were able to set up a simple system fairly quickly. From the washer, water goes to two storage barrels that have free-flow irrigation hoses hooked to them. The hoses go snaking along the property, through fences, under paths, around landscaping to drip on all of our ornamental borders. Yes, we use eco-friendly soap. No, we don't use the water for anything we're planning to eat. With five people in the house, it's easy to do at least one load of laundry a day, more often two. Which, coincidentally, is the exact proportion to fit on our newly-installed clothesline. We'll just pretend we planned it all that way.