If you want to offer your guests something a bit more luxurious than a floor to sleep on check out the Instant Bed-From-A-Box.
When it’s not needed the spare bed can be stored at the bottom of the wardrobe like any other box (measuring 24″ L x 16″ W x 20″ H). Then the next time one of your mates gets a bit too phi-shed to drive home you can wheel the box out, power it up and watch the mattress inflate and the legs fold out giving your mate an actual bed to sleep on rather than an inflated mattress on the floor (if he looks a bit sickly you’d probably be best letting him sleep outside, the fresh air will do him good :)).
The firmness of the bed can be controlled at the touch of a button and can support up to 300 lbs (though you may not want to let any amorous couples share it). The Box-To-Bed is available from Hammacher for $250, there’s meant to be a video of it in action (from box to bed, not amorous couples) on the site but I couldn’t find it.