There is a new open-source unbiased rendering engine in development, called Luxrender. The images produced with Luxrender, simulate light using physical equations. This means extreme quality and real images. And guess what? The developers are planning to make Luxrender integrated with Blender!
They already have binaries for Linux, Windows and MacOsX. Interested? If you want to check out Luxrender, visit their official web site to know more about it.
And here is a very good tutorial, showing how to render a scene created with Blender.