A real time ray tracer from the demo scene:
http://www.realstorm.com/

And comments on it:
http://www.acm.org/tog/resources/RTNews/html/rtnv5n1.html#art3

Stanford research on real time ray tracing with
the next generation of consumer graphics cards:
http://graphics.stanford.edu/papers/rtongfx/

(thanks to PEB for the pointer)