I don't know if this has been mentioned before. I saw a post on it in the Exp. Portal Forum. It is a simple shower head that will screw on to just about any 1 or 2 liter bottle.
It also fits some water bladders like Platypus. If you are interested, here is the post from the inventor: http://www.expeditionportal.com/forum/t ... ght=shower
Looks like a great gadget that will be useful for backpacking and car camping.