This is a very good tutorial that covers Yafaray with great clarity. The tutorial is created by Mr Ira  Krakow who runs a forum dedicated to Blender 3D.

About Yafaray, it is an open source raytracing and global illumination renderer. For this video, it is used together with Blender 2.49. Yafaray extends Blender’s rendering capability by including Global illumination which is not available in the latter.

Yafaray is not limited for usage with Blender. As of this writing, it can also be used together with the latest version of Truespace which is version 7.61.