A good idea for a small bathroom, under hanging shelves for things like cotton balls, cotton swabs, etc. Also great in the kitchen, for a spice rack over the stove. Just hang jars from bottom of the cabinet.
a hinged full length mirror from IKEA (Stave mirror - that is x hides jewelry storage -- brilliant idea from The Girl on the Go! I would use a thin sheet of plywood cut to fit behind the mirror so I don't put so many holes in the wall.
Hair Appliance holsters: Use hook-and-loop tape to attach lengths of diameter PVC pipe to the vanity door to hold the curling irons. Do the same thing with pieces of pipe to hold the cords. Let your curling irons cool before you stow them away.