We all know that Flash renders our MBAs almost as slow as a Windows machine (hehehe, just kidding) and the most common source is YouTube. Check out http://www.joeyhagedorn.com/2008/04/16/youtube-in-mp4-via-quicktime-plugin#comment-123434 and get Quicktime to play your YouTube videos (when the higher quality version is available). I think that most have MP4 versions already considering that the iPhone uses QT engine.