Typically the worst part of the school day for me is that period at the end of the day when the bus bell rings and you are waiting for the car riders and walker/bikers to be dismissed. I'm sure it only lasts less then ten minutes but it feels longer and I swear I age ten years in the process :)
In an attempt to keep the class focused during those long minutes I started playing Steve Spangler on Ellen Videos that I downloaded (using the YouTube downloader written about here). The kids love the humor and look forward to seeing what kind of science Steve uses to make Ellen laugh. The videos last anywhere from 7-10 minutes and are perfect end of the day fillers.
I would highly recommend watching them before showing them in class to ensure the content is appropriate for your students.