Folding Bedboard. Unfold this 1/4" thick bedboard and slide it between your old, saggy mattress and box spring...your lower back will thank you! Better than a sheet of rough, heavy plywood, because you can fold it to 30"x15" for easy storage, and it won't ruin your bedding. Vinyl over thin wood board, not cardboard like many competitors. Unfolded, it's 30"x60" for a twin bed; get two for a queen size bed.
Snap 'N Stack™. If you pile everything in a cardboardbox, you risk crushing a good many of your decorations. Instead, use a hard plastic Snap 'N Stack™ to keep everything organized and protected from dust and damage. These plastic storage totes have clear sides to allow you to see what's inside at a glance.