While perusing Canadian House and Home, we found a how-to for a very involved (for us) DIY headboard project. The instructions called for creating a frame out of two-by-fours and attaching plywood, resulting in a tall, door-like headboard. Being the carpentry-phobes we are, we thought, "how about using an old door and cutting out the middle man?" We're not the first to think of it.
Junk Market Style posted this garage-door turned headboard, which is a coat of paint away from Canadian House and Home's project (below), but perhaps a bit easier: