A new physically-based renderer is on the scene called Luxrender. What separates this one from the others, you ask? This one is GPL, Open-Source.
LuxRender is a new, open-source, free software rendering system for physically correct, unbiased image synthesis. Rendering with LuxRender means simulating the flow of light according to physical equations. This produces realistic, photographic-quality images.
You can download it from their site, v0.6, with plugins for Maya, Blender, XSI, and Cinema4D.
via Lux Render.
