If you have no idea what to do with those simple toilet paper rolls, there are plenty of ideas on internet or here on Recyclart. My idea is simple and easy, I came up with it while I was studying german and I needed a system to have my new words sorted to learn them.
It's so easy! You just have to cut through the cardboard (vertically) to open the roll and either paste it or screw it on the wall, and there it is, a mini shelf for your notes. Could work for anything light weighted you need to organize. Hope you like it and inspire you to make more complicated things reusing this simple material we all have at home ;)