This is something I have wanted to try for a long time, but never got a chance to do. Yesterday, I managed to get Mosix running on a couple of machines. One of the machines is about twice as fast as the other so I don’t think it is an ideal environment, but worth the knowledge I gained. When a cpu intensive process is run on one node you can see the load shifting to the 2nd one, though ‘top’ doesn’t see any difference.
Scyld seems to be a better solution for clustering, but it isn’t free. I think they have a stripped down free version, but I couldn’t find it.