Mess Free Painting with Egg Carton - have used this system in my art room for years! Best bit is that the egg carton lid stops the paint from drying out between classes even over a whole week - if it's not excessively hot!
Popped Bubble art: Simply color bubble mix with food coloring and blow bubbles onto paper - as the bubbles land and pop, they create beautiful works of art. It goes without saying that this project is best done outdoors. A great one for those lazy summer afternoons.