Let's say you wanted to make a light painting video, normaly this would take thousands of well made freehanded light painted pictures taking 8 mins or more to create. Now a free and open source plugin to kdenlive (a amazing video editor) fixed that. I know i sound like i'm trying to sell something but i'm not. Try it yourself!
http://vimeo.com/granjow/lightpainting2that's the vid that was created using the plugin.