The first URL to check for Debian Beowulf is the archive of this list, starting at: http://lists.debian.org/ . Your question is a very common one on this list.
For that reason, I put together a couple of simple things at http://lyre.mit.edu/debian-howto/ which is far from complete (contributions welcome) but may answer one or two of your questions.
Also check out the Debian Documentation Project linked from http://www.debian.org/ which has the beginnings of a system administration guide.
I agree with Adam... in fact, in anticipation of reuniting DeBUG this coming semester, I am going to put my ClusterFAQ up at http://www.extreme-linux.com/, probably next week after digesting Adam's HOWTO. The SMP / Linux HOWTO as well as the redoubtable Beowulf HOWTO are getting a little long in the tooth; they don't mention anything about the 2.4 kernel, for instance.
