HTML5 is as powerful and cool as a nuclear powered chainsaw. A mix of the new 'Canvas' tag and javascript means that you can create some very cool things right there on the browser. I've been waiting for some people to create some cool things to prove my point and Canvas Rider is a good example. The idea is not new but the fact that no flash is required fills me with trouser twitching joy.
Be warned: it's addictive.