Beowulf clusters and personal supercomputers
(my thanks to Courtney)

microwulf
-This one seemed particularly interesting. It's a super small supercomputer; it's also quite cost effective.

beowulf tutorial
-A 'how to build you're own beowulf system,' courtesy of cal tech

beowulf book
-In-depth coverage of beowulf systems (history, hardware, parallel models, building a beowulf, etc.)

clusters
-Mr. Mike Perry describes the system he built for The Illinois Genetic Algorithms Lab (mostly maintenance and use of the cluster)

hampshire - lee spector
-A beowulf cluster at Hampshire College. Not very detailed, though.

book by MIT press
-A book by MIT press entitled Beowulf Cluster Computing with Linux, 2nd Edition. Looks like it would be highly detailed.

buying a cluster
-This is a commercial site, but it seems like it has some good (although maybe basic) information. You can request a quote (how much a cluster would cost you given x, y, z, etc. variables), which is interesting.

Beowulf - HOWTO
-Step-by-step instructions on how to build one's very own beowulf cluster. Very detailed with some troubleshooting information.

detailed Beowulf - HOWTO
-More information on how to build a beowulf system from one of my favourite websites (wired.com)

(my thanks to Candace)

Wikipedia
-History and links

Beowulf.org
-The Beowulf community

another Beowulf - HOWTO
-How to build one's very own beowulf cluster.