I knew those styrofoam squares that came in my sausage study packaging (so fun to be paid to try out different kinds of sausage!) would come in handy for something. Apparently, they are the perfect thing for a simple, unique art form that I discovered from Jellyfish Jelly (who, by the way, has a great blog full of crafty ideas for uncrafty parents).
Using a sharp pencil, you can poke small snippets of fabric into styrofoam to make a picture or just a pretty pattern. It's very easy and makes for a unique effect. M was able to do it without too much trouble.
The concept also works with crepe paper if you fold it once or twice. (Don't mind the extra "decoration" - just par for the course around here :-)
If I had easy access to styrofoam balls, I think it would be fun to make some pretty rainbow balls for tossing around.