Oliver Couston has created a great guide, showing the workflow from Substance Painter to Arnold.

I got some interesting results connecting texture maps to the UV Coords of an Ai Image shader recently.

A tutorial that shows the basic workflow can be found here.

Arnold Kicks Ass

Zeno Pelgrims has created a shading community website that will host monthly material challenges, and will be used as a place to talk about shading/renderers/algorithms in general.

www.shaders.xyz

Mostafa Azab has a free Standard shader pack available for C4DtoA.

Maximeroz has an excellent HDRI pack available for free.

Here are a couple of test renders I did of the new physically-based hair shader coming in Arnold 5. Model and groom courtesy of Zeno Pelgrims.

MAXtoA Version 0.9.608 is out. More information here.

Saber Jlassi has created some incredible pyro simulations, rendered with Arnold for Houdini.

He also has a youtube channel with Arnold rendered pyro animations.