Corrugated Construx building system
Laser cut building system for maker spaces. Just use amazon boxes or other 1/8 " cardboard, paper straws, and your imagination!
I work at a Children's museum and often wish I had a larger materials budget. This is a wonderful and cheap (assuming you have a laser cutter) solution that let folks build and take home their projects.
Feel free to edit, add, and create your own within the standard!