Here is the link. Check it out. There is a lot of different kinds of materials, some of them very good.
*Update: Vray for SketchUP has recently been purchased by Chaos Group. Therefore, the original asgvis site has been relocated to Chaos Groups website. I have not yet found where the materials are now located (if they are still around at all). I have located a new library of materials. See the link here. You can also watch my video below to see how to make your own Vray materials.
Feel free to check out all our other Vray and Vray for Sketchup resources.
Here is a video tutorial I did that goes over all the basics of Vray Materials, so you can learn to make your own.