I was reading an article in a PC mag entitled "Build your own supercomputer" but as it turns out it was mainly supercomputer history and then talking about basic multiple core PCs which are more powerful than a $10 million Cray from the early 90s. The end of the article though was a lot more interesting. It was about using bog standard PCs to create a linux cluster to do some serious number crunching.
All you really need is a bunch of old PCs, a switch or two and the software to run it all. The PCs can be pretty much anything as long as they have a COU, RAM and a network card. The next step is to make sure they are linked up to the switch or switches to optimise the communication speeds between the different boxes. After that it´s just a case of installing the software (all of which is free to download since it´s open source) and configuring the entire system.
I also want mine to be able to run with one machine on a UPS and set up so that if one or all of the others go down (either due to power failure or hardware failure) it will keep running as a system and when the other systems come back on line they will just boot and join the cluster again. I´ve got a lot more Googling to do to find out how to do all this and if all of it is possible but I´ll post more here when it gets done
I'm a web developer based in the East Midlands, UK and if I keep up the current rate, I might have developed 3 million sites by the time I retire