1. Do the Circulation by Schoolhouse Rock
2. The Circulatory System by Study Jams at Scholastic
3. Make Me Genius's Circulatory System*
And finally, one that's a bit more complex for the advanced students and adults who love to learn. Crash Course in Biology's video as posted on YouTube...
Technically, this is both the Respiratory and Circulatory Systems, so you can skip ahead to around 5:40 where the Circulatory System starts up and then come back here in the future when we're studying the Respiratory System so you can watch the beginning. Up to you!
In addition, here is a link to a special on the heart created by NOVA that includes an interactive animation of the heart as it pumps blood so you can watch the motions it makes (for the squeamish people, this animation is very tame and completely animated, so there is no gore to it).
*This video has some (slightly humorous) sound issues and a couple spelling errors, but it does offer a lot of good information if you can overlook its flaws. What do we expect for free, right? Ha. Teachers: You may wish to use the spelling errors as an opportunity for learning! See if your students notice them and can give you the corrections.