My friend in the room next door challenged me with this project. He needed some way to hang his backpack. Originally he wanted to use 3M adhesive hooks, but these didn't stick to the inside of his closet. The strength of this setup depends on which hanger you choose and how many rubber bands you use.
Step 1: Requirements
A. 10-15 rubberbands about 1.5 inch diameter
B. Somewhat heavy duty hanger
C. Hanger rail
Step 2: Construction
Place all of the rubber bands on the furthest shoulder of the hanger. Place the hanger upside down and under the hanger rail. Gradually pull all of the rubber bands over the rail and over the closer shoulder. That should be about it. The more rubber bands you use, the stronger it should be.
While a hanger could possibly be used normally, I find this method to be the most convenient because there is only one handle to worry about hooking.