I made two of these, outer space for Leonard and scotty dogs for Rachel. Now I need to make myself one, because these are way better than what I am trying to use. You put the drawer liner between your mattresses, then you can put books, lotion, pens etc in the pockets.
You need a piece of rubber drawer liner and a length of fabric as wide as you want your organizer to be (I used 1/2 yard for Rachel's and I think that was the best - 18 inches x fabric width (40-44 inches)). This takes about 10 minutes if you iron.
Fold the fabric right sides together along the factory fold with the selvedges together. Sew along the two sides and turn right side out. Press. Fold up the bottom end as deep as you want the pocket (mine is about 8 inches). Iron, then topstitch in place along each side, then stitch where you want to divide the pockets. Insert the drawer liner into the open top. Fold down the raw edges on the top (should be the selvedge) and pin with the drawer liner in between them. Sew along the top edge, enclosing the drawer liner. Ta dum!
I got the idea here, but my way is easier and looks just as good and doesn't use as much fabric or expensive notions.