Although no waste is preferable I'm always interested in clever ways to extend the life of a product that will eventually become waste via either recycling or landfilling (in this particular case, the former is the best although, unfortunately, not always the case).
With Yun Hwan Sung's 'Seeds in the Bottle" design concept, an ordinary, inverted plastic water bottle becomes an instant herb garden with soil and water. I'm not sure how well this would fly in reality but the idea behind it is pretty nifty ... kind of an updated, high-design take on cutting the bottom off of 2-liter bottles and using them as planters.
What ways have you extended the life of plastic beverage containers around the home and garden? Piggy bank? Potpourri holder? Bird feeder? Toilet tank water conservation device?