Balloon Rockets - I've done this in several science camps I've conducted. Kids have fun with it. But, when the balloon deflates it may fall off the straw because it's surface area changes - another good thing to show and explain to kids.
Use milk bottles for pencil storage Recycle plastic milk bottles in to pencil holders. Grab a craft knife and recycle your large plastic milk bottles in to pencil holders. Extra points if you go all OCD and file them by colour.