I've personally replaced about half the windows in my home with new ones (See How to Install a Sash Replacement Window) but haven't yet thrown away the old ones. What to do with old windows? Use them in the garden!
I spotted these windows and doors in my neighborhood while on a walk. Some windows are being used for starting seeds, others as the tops for a mini greenhouse, and one old screen door as an entry way into a simple gated garden. I've been tempted to put mine to use but haven't yet had the need.
Have you been able to put old windows to use in your home or yard?
(Images: Trent Johnson)