PMI used to have a quite active email discussion group, but it disappeared a while ago, and they apparently are taking their time in getting it up and running again. I wonder if they need some help managing the project.
;-)
But there are other venues. For general discussion of project manangement issues via email, I like the Newgrange discussion group.
For discussion centered on the Critical Chain approach, allow me to guide you to the CriticalChain discussion found on eGroups.
As a matter of full disclosure, I launched the CriticalChain list.