There are a number of mechanisms for building distributed or "clustered" FreeBSD systems.
There is of course the freebsd-cluster mailing list where you would probably get some more technical responses than this list. Here is a site I quickly Googled up regarding a Beowulf cluster running under FreeBSD: http://blizzard.rwic.und.edu/~nordlie/miniwulf/ Is this the sort of thing you had in mind? Aren.
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