Thanks to +David Fink for pointing out Animation for Kids. In the past, I have done work with students on Claymation projects, but this web app makes animation accessible to an even larger group of students.
Some of the things I liked about Make an Animation was no log on needed, simple to advanced functionality, and ability to save gif to computer. Make an Animation is designed for one setting which could be a negative for more complex projects. In either case its a solid introduction to animation which could serve as useful background information for more complex projects.