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.
Newtons Third Law: This isn't an industry rocket, but can be called a rocket because it uses the same principle. Gas is expelled from a nozzle at one end of an object, generating thrust, which moves the object forward. The "fuel" this rocket uses is air.