This little info (http://www.heise.de/newsticker/data/law-18.03.03-002/) is about some german scientists showcasing computer cluster with realtime raytracing capability. Main claim is 10 fps with various effects (sorry, no time to dig this).
This was demoed at Siggraph as well. It's impressive, but it requires a large cluster of beefy computers and I noticed quite a lag when I tried it. It looks like it's almost ready to be useful for some large companies with deep pockets like car manufacturers.
In the news they said only 11 Athlon PC are used to archieve 10 fps. However, the clock rate was not mentioned. If they uses 2Ghz CPUs, the theoretical performance will be around 88GFLOPS (with SSE).