mac <-firewire-> mac <-firewire-> mac
etc, and if you have a firewire HD, make sure it's connected to 1 mac.
then go 2 network prefs and add firewire as a network-connection on each mac. rendezvous will do the rest for ya.
adding firewire: in the "show:"-dropbox choose "network port config", the choose "new", name it firewire and choose "built-in firewire" as port.
cheers.