Writing mental ray Shaders has at last been published. This third volume in the series of mental ray handbooks is a tutorial introduction to shader programming. All the software and scene files discussed in the book are available at the book's website. The book also includes a CDROM that contains a fully functional version of mental ray.
You can use this forum to discuss Writing mental ray Shaders: ask questions, discuss topics the book raises, and report any errors you may find. Based on the posts in this forum, I'll add material to the book's website to correct and augment the book.
I hope you find this book a useful introduction to shader programming in mental ray.