I like this, basically the author took vinyl drywall corner bead, and screwed it into the bottom of a shelf. The bead has holes in it that can be used to put s-hooks in to hang stuff. The bead is a little over $1 a foot, and you can get 100 S-hooks for $8.
http://www.instructables.com/id/Double-Duty-Shelving-with-Cheap-Hanger-Hack/?ALLSTEPS