If you have a really small room and need to have a way to open it up some for day time or just to have an extra bed for sleep over guests. Ana White has an awesome diy Murphy bed that you can make and then that small room will have more day time space or the sleep over guest will have a bed that is not in your way every day.
PLANS: A Murphy Bed YOU Can Build, and Afford to Build
http://ana-white.com/2010/03/plans-a-murphy-bed-you-can-build-and-afford-to-build.html