I have just recently discovered a new app - Shadow Puppet.
The students take pictures using the iPad camera. Then they insert the photos into their Shadow Puppet creation. The children narrate their way through the pictures. Here's how my students used it.
They were given this math problem:
This app is excellent for students to explain their thinking. And it is FREE!!!
(I couldn't post any of my students' videos. They all took a picture of themselves and inserted it into the finished product. Funny kids!)