This page has some notes about the isc.FreeBSD.org cluster.
as of 20120522, this page is quite stale.
Ideas for new hardware / use of systems
Mainly for VLAN support, to be able to segment the LAN for security.
E.g. HP Procurve 2510G-24.
A standby / extra www.FreeBSD.org server for redundancy.
All systems should be 1 or 2U rackable servers and have a low power usage. BIOS serial redirect support preferred.