Whenever a recipe calls for green onions, the Dutch part of me starts to grumble. I can never use the entire bunch before they get wilted, and it seems so wasteful (even though they cost approximately 30 cents). I recently learned, however, that you can grow green onions in nothing but water!
Simply cut the onions down very close to the white part and place in water (make sure to change the water every couple of days). After about a week they'll be a good size, and you can use them as needed. If they start to grow too big, just trim them down to ensure they continue to grow. They won't last in water alone forever, but should keep growing for a month or so.
They also make a nice addition to a kitchen windowsill!