Not raytracing, but anyway.. I just had a look at Debris - the Farbrausch entry at Breakpoint 2007 and well:
Pretty good use of 180k, I'd say...
One or two of you may take an interest in Werkzeug - their texture generator.
For some demos that actually do ray-tracing, rather than hardware accellerated stuff, check out the old Nature sucks series at www.realstorm.de