This article titled "How To Grow Sprouted Onions" at Alternative Gardening talks about exactly that. I had no idea. All this time, if I didn't eat an onion in time, I would simply plant the whole thing as-is in the soil.
How to Build a Rain Barrel. A dual barrel system that uses atmospheric pressure to equalize the water volume in both rain barrels. Use the water from your rain barrels to water your plants.-----great idea and can help save money!