Similar to other forums, I think that I would be a good idea to have a thread about useful links & resources.
I'm going to include references to the Yafray wiki as well, the idea behind is to multiply links to those documents. I think that it is a good idea also to include references to generic documentation about raytracing, as well as links about photography and optics, papers about new researches, links to other interesting forums and to other Yafray tutorials and useful forum missages scattered all around the web (yafray forum included).
YafRay developers can join us as well and post links about their researches and other development questions. Anything you think is useful.