Also look at a presentation on ddraid done by Daniel Phillips of Red Hat. He's basically written a clustered RAID server that copes with (up to) entire box failure. There are also a couple of distributed load-balancing file systems, like Lustre, which can do similar things.

But that may be only one aspect out of what you're wanting out of your cluster. What are your requirements? What software packages are you needing to run? What sort of network do you have in place?

Have fun,

Paul

P.S. This was one of the cool things about being at the 2005 linux.conf.au.