Mostafa Azab has a free Standard shader pack available for C4DtoA.
Maximeroz has an excellent HDRI pack available for free.
Lee Perry Smith has done some cracking skin shading tests rendered with Arnold for Maya.
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.
Thrilled to see my colleagues at Solid Angle win a Science and Engineering SciTech Oscar award. More information here, here, here and here.
Zeno Pelgrims has updated his camera shader for Arnold. It is capable of simulating optically imperfect lens effects.