HOWTO make a Joule Thief and get all the power you've paid for

This wee beastie is a Joule Thief, a device whose sole purpose in life is to exhaust the power remaining in batteries that are too weak to do anything else. Simply build these and affix them to your "dead" batteries and thrill to the spectacle of the power you've paid for being available to you, right down to the last dribble.

Make a Joule Thief (via Red Ferret)