This is the experiment/project I often use myself as testing ground, and I decided to put it online.
Oh, and it's a WebGL shooter style game that uses a whole lot of HTML5 APIs.
Come on, shoot at balls right now over here: http://jensarps.github.com/shooting-at-balls
It is an offspring of the Ascent Project, but it also features elements not present in Ascent, such as InfiniteGround, the WebAudio API or PageVisibility API.
This experiment only works in Chrome.