Stop motion is a lot of fun and there are many free apps out there. Those with Chrome books have one from the Chrome store - stop motion animator. On apple there are several free apps - we used imotion, but there are others such as 'I can animate,' 'Stop motion studio,' 'Lapse it' etc
Stop motions take patience and perseverance, and can be done with anything. They can be as simple as making a sock look like it's moving across the floor, to more complicated animations such as Aardman's Wallace and Gromit with facial expressions etc.