Nail up an old AT computer case on the wall to hold your junk.
Step 1: Attach nail
I had an old computer case which would not hold the new ATX board. Rather than throw it away, I put it up on the wall so that at least some of my junk can be kept off the floor.
The first step is to hammer a nail into the wall. I was not allowed to, but luckily there were two nails already in that wall. So I decided to do a hanging shelf on a single nail. To hold it steady sticky tape was fixed to the wall at strategic locations. This helps the shelf stay in place even when loaded unevenly.
Step 2: Add shelves
Now that the frame is up, I need shelves. Old circuit boards with all components removed do the job very well.
Step 3: Load it up
Stack your junk on it. And that is about it.
You can attach various other storage units to this, limited only by the carrying capacity of that single nail.
Step 4: Another version
The photo shows a previous incarnation, which I took down in order to clear vertical space above my desk.