A couple of people are working hard to make this easy with a centralized configuration service that lets you assign all the ports in one place for all the servers on a machine (as I understand it). I think this will be in 3.0.1 which will probably be released next week. Meanwhile you can track its progress on the dev list and in cvs.
Thanks David, this sounds promising. Unfortunately for me, I have to do a release into production this week and must have two instances of JBoss on the same box. If anyone has any step by step directions of what needs to be done, it would greatly be appreciated.
Hey, I finally got it to work. If anyone is interested in what files need changed, it is: