I have played with render to texture to generate particles with physics, the idea is to compute particles position on the gpu and use it as input to render them. For this I have use the firefox logo in 512×512 so we have 262144 particles animated even if somes are invisibles. You can find some useful information from this articles http://directtovideo.wordpress.com/2009/10/06/a-thoroughly-modern-particle-system/
Ideally It would be great to have render to texture that support floating point for webGL, but without that I did a 16 bits precision with two textures ( high bits and low bits). It’s a bit boring, in fact It breaks me to try more effects, I would really like to have render to texture with floating point support.
To get a WebGL Implementation have look to Khronos instructions http://www.khronos.org/webgl/wiki/Getting_a_WebGL_Implementation
You need a browser able to run webGL to try the realtime version http://plopbyte.com/webgl-particles-demo else click on the image to show the youtube video.