This script hooks your particle system up with a camera automatically, resulting in a z-depth/focus depth/height/age/etc shader, that can be used to render images meant to serve as an aid during compositing. This way you can e.g. render out hardware particles' depth channel with motion blur. The script has been tested on Maya version 5.0 and 6.5.

Except being able to render the particles in the hardware batch renderer or hardware buffer you can also use other renderers such as Pixar Renderman. Note that if you want to render using Pixar Renderman, you will need to light your particles. One way to do this could be to just orient constrain a directional light to your camera.

Version history:
1.1 - The script will no longer delete any already existing expressions in the scene.
1.0 - Initial release.