Cardboard garbage boxes
Instructables user dontstop1990 built this clever contraption to save space in his dorm room. It stacks three trash cans and angles them for easy disposal, and even includes some cardboard wall hooks to keep it from tipping over. He doesn't include very detailed instructions, but it basically just consists of cardboard and duct tape, so it shouldn't be too hard to figure out from the photos.
Even if you don't live in a tiny dorm room, the tower would be great to stash in a pantry or utility closet, and you could easily improve it up with a coat of paint and adhesive wall hooks to keep it standing. Check out the source link for more photos to get you started.