Why didn't I think of this? Pick the size & fabric -- DIY Memory Foam Rug via the idea room, love this! Another note - memory foam rugs are beneficial to those of us who have brain injuries - no tripping and falling!
DIY Glitter Magnets - an easy craft idea for kids too. J in the Library's note: Though glitter is almost guaranteed to be messy, this is a relatively easy project that would only take 2 library classes, or 2 meetings of a maker club.