TreeHugger has shown many ways to hide the bed; most are designed to gain more space. But the Red Nest by Paul Coudamay doesn't; the bed is still there taking up space, but is hidden by the sliding bookcase.
Love this play area over the bed, like the anti-loft bed. I think I& leave off the first couple of steps of the ladder and make it a safer place for the older kids to play with and store their LEGO creations. (Apartment Therapy with loft bed inspiration)