Build stackable shelves using the free plans at the link. You will also make your own jig to make this project go smoother. It is easy to assemble once complete.
Here are the free plans to build a back of door shelf. Perfect for a pantry door or closet door. You may have to alter the dimensions to fit your particular door. Should be easy to do.
This storage shelf unit can be modified to make it longer or wider. It is perfect for behind the door in the bathroom or perhaps the childrens bedroom. Free building instructions available at the link.
Build this small open shelf unit using either recycled lumber or new. Beautiful. Here are the free woodworking plans.
Here is a tutorial to build a shelf unit for the bathroom although it could easily be hung in any room. Free plans at Shanty2Chic.