This plugin is no longer maintained.
You provide a list of youtube videos, install the widget in your sidebar, and your visitors get a randomly selected video with each page load. You set the width of the video to work best in your skin, and optionally settings to do your own html markup for the title. Oh and you can set it all up to be instance-specific settings if you're into that sort of thing. I like settings! I'm into that sort of thing ;)