Produce an animation.
GoAnimate - A private and controlled environment where your students can easily animate with an endless cast of characters. 1 teacher + 100 students = FREE. $12 per year for unlimited accounts under the same umbrella.
KerPoof - Disney-owned; Create animations, pictures, artwork and more. Mostly free site, with premium options available. Teacher accounts are free.
Zimmer Twins - With easy-to-use movie making tools, kids can create awesome shorts complete with animations, talk-bubbles, and sound clips!