[BHSPitMonkey]

For what it's worth, I wrote a simplistic Osmos clone last year using 2D canvas drawing (not WebGL). It's fairly inefficient, but anyone's welcome to hack on it and make something cool with it.

http://stepheneisenhauer.com/demos/browsmos/

[p0nce]

Well you can render many spheres with tiled rendering.

http://www.gamesfrommars.fr/demojsv2/