not worth it, imo...
specially since the PS3's memory is sh!t, and a bad bottleneck.
anyways, here's some clustering help links and other resources, including a small cluster video, good luck.
http://www.ps3cluster.umassd.edu/index.html
PS3 Real-time Ray-tracing - YouTube
http://www.ibm.com/developerworks/li...GX03&S_CMP=EDU