Simple designs scratched into foam trays (from deli or meat market) by mealisab, via alisaburke.blogspot. Works great with thickened dyes and textile paints. Ask your local fish/meat market for some and they may just give them to you. Great fun.
If you have a foam or polystyrene container (say, from taking home leftover food from a restaurant), Total Art Soul gives us this upcycling idea: Turn it into a stamp for printing. Materials needed: An empty container, a pencil, ink or paint, and a small roller. For the super-simple how-to / tutorial, see the Total Art Soul post here. [Thanks, Mayme Fravel, for sharing the link on the Unconsumption Facebook page!]