YafaRay
YafaRay is an open source ray tracing program available under the LGPL license. It supersedes YafaRay (Yet Another Free Raytracer). It enables the creation of images and animations to a photo-realistic quality.

YafaRay
A guide to the open source Ray Tracer.
Yafaray was developed in C++ and can be ported to a number of operating systems including Linux, Windows, and Mac OS.
It has a number of rendering features including: global illumination, skydome illumination, caustics, depth of field and blurry reflections.