Wow. I kept seeing people mention subsites on the bboard, but had assumed that it was simply another way of referring to mounted applications under different URLs. It seems like things are far more powerful than that.
I will definitely want to give a different look-and-feel to different subsites, and the ability to change the master template will definitely make that pretty easy. Between that and different CSS stylesheets, we should be just fine.
Believe it or not, permissions will be important. The umbrella organization wants to be completely sure that the individual member organizations won't have access to each other's data, except when explicitly allowed. But once I learned about the subsites, those worries went away.
As for the site-node mapping, that seems to work for URLs within a single domain. But what happens if I have different domains, each of which should point to a different URL inside of my OpenACS site? (Or do I just need to read more documentation?)
I keep telling people that everything you want is somewhere within OpenACS, if you look hard enough...