Cereal boxes turned mail sorters (covered in wrapping paper) and attached to the wall with velcro! I thought this would be neat in the classroom - organize different kinds of paper, handouts, etc. Or use as mailboxes for the parents.
For organizing file folder work jobs! Dish drainer used for organizing files, etc. The cup in the corner could be used for pencils or dry erase markers (if your file folder games are laminated). Or take the cup off completely.