VrayforC4D documentation
VrayforC4D on Vimeo
VrayforC4D Intro Videos
docs.chaosgroup.com
There's a lot of useful info on the Vray 3D Studio Max site that isn't in the official VrayforC4D documentation.
Useful Forum Threads
Displacement
Vray Shaders
Vray Dirt
HDRI Usage
Cameras
Vray DMC Sampler
Multipass Rendering