Store your sandpaper in a three ring binder. Just uses some pocket folders to keep the sandpaper organized by different grits in the binder. Label the binding of the three ring binder "Sandpaper" so that it's easy to see when sitting on shelf.
Keeping Track of the End of Tape
Organizing Your Bills
Keeping Track of Socks
Organizing DVDs
Balancing and Organizing Your Checkbook
Organizing Your Meals