Hoping others will add to this... I'd like this section to stay focused on renderman as it relates to maya, there's several sites already for pure renderman. Here's some links to a few:
What they mean is not really a script, as much as a function. I have just done a render where i want to pRef from a deformed object, but not include all the deformers. Basically i have a blendshape that then is deformed by bones. Now i want to pRef the original blendshape, after the bone deformation, and then render the other blend shape with the bone deformation on there. So i wrote a quick script to do all this,and put that in the pre frame field in mtor... no use... it didnt work. So i saved the script in a file and sourced that from the pre frame script field, and by magic, it works!! ahhh nice.
3delight from v9.0 onwards supports the misss_* shaders. Though not all attributes are translated, it works nevertheless. It also supports few other mr hypershade nodes like the car paint, metallic paint and glossy reflection/refraction nodes.