The sticky section got too messed up, so I collected posts that contain good tutorials and resources in this separate thread.
mental mill shader pack 1.0
This shader pack provides some more shaders with some utility functions that you can not find with the default shader set of mental mill. Read the .pdf file that comes with the zip file for a more detailed description.
mental mill 1d Curve Function Shader Pack
A shader pack providing Function curve shaders that can be used for animation inside a shader and to drive texture generators that come with the same shader pack.
Water shader study in mental mill
Here you can see a shader study to create a water shader that is rendered on a flat plane.
Using mental mill Phenomena in Maya 2011
In this small tutorial you will learn how to get a Phenomenon that was built in mental mill 1.1 running with Maya 2011
MetaSL shaders in Maya 2011
For those working with Maya 2011 there is a good tutorial on how to get MetaSL shaders to work with the mental ray renderer.