Nice multifunctional designs—some production, some concepts—from the Belgian design studio of ID'er Alain Monnens, Idam Bvba:

The FlipTable (above) is simple, stackable, and flippable, tipping from desk height to side-table height.

The ServiceBin (manufactured by Wild Spirit) is a stool, or a wastebasket, or a storage bin, or a planter, and the top pops off to become a service tray.

The Bench 360 also is meant to be tipped, going from a curved seat for many to a rocking chaise longue for one.
The projects aren't directly linkable due to Flash (grrr) but you can see more of Monnens' projects here.
Comments
That FlipTable thing would bounce around, it's like a diving board. Looks like if you got up too fast it might catapult all the stuff off of it.