I'm interested in pc clustering as a hobby, but I don't even know where to begin. Help anyone?
puke:

Clustered Systems are usually designed for High Availability;
continued service when component(s) fail.
Some are special purpose/high performance designs.

Here are some references for your reading on the subject:
IMB HACMP (http://www-03.ibm.com/systems/p/software/hacmp.html)

high-performance cluster systems (http://www.enterprisenetworksandservers.com/monthly/art.php/687)

AlphaServer cluster with reduced risk (http://h18002.www1.hp.com/alphaserver/products/clusters/es40cluster.html)