I received this link on one of my mailing lists and thought it was the greatest thing since sliced bread. Following up on my "Flash is dead" post, you can enable Youtube.com to work in HTML5.
Go to: http://www.youtube.com/html5 and you can "opt-in". I assume it places a cookie in your browser so that every time you try and view a video, the video plays in html5 instead of flash. My browser doesn't run at 100% CPU or anything. It's awesome. Go do it now, help kill flash.