Recyclables in a makerspace are crucial. Not only are they cheap (if you do it right, it costs nothing), they also offer great options for prototyping. Since they are easily available and not made of precious materials, they can be used freely and frequently.
Here are three of my favorite recyclable materials for prototyping in a makerspace. All three; plastic bottles, cardboard boxes, and packing styrofoam have their own distinct characteristics, therefore can suit a wide variety of applications and projects.
A water bottle's slick plastic material is perfect for mimicking glass. One liter bottles offer a nice clean middle which you can cut out and lay flat. It also takes spray paint very well, although drying time can be lengthy. Small water bottles are soft and can be easily cut with scissors by just making a slit with the tip of a knife, then inserting the scissors and cutting the desired shape. Larger bottles tend to have thicker "skins" so using heavy gauge snips will give you a better result.
This is a great material for prototyping because of its versatility and low cost. Its strong, easy to manipulate and to cut (see my article on cardboard techniques). It's corrugation makes it ideal for holding a fair amount of building weight, so it can used to prototype and construct bases. And if not in the best of condition, can serve as a gluing mat or a spray painting booth.
This enemy of every environmentalist is still around and still used widely by companies as packing material. Varying degrees of density, shapes, and sizes are available. It's a perfect material because its easily cut, usually with a serrated or electric knife, and because of its light weight. As soon as you put out the word that you're collecting the stuff, you'll notice how eager people will want to give it to you to ease their guilt of putting it in the trash. Be prepared to receive a wide variety of odd shapes, but it's all good in a maker's world.
These three throw-away materials should be among your other materials in your prototyping or recycled materials carts. They are cheap, easy to get, and offer students and makers a great variety of choices. It's also a great way to use something that would otherwise go to a land fill.
Here's a peak at my recycling materials storage. The amount of materials varies depending on donations and need. I try to keep it tidy, but like everything else, it's a constant battle.