Let's see.. the first thing you'd need was a way to match people up--some sort of searchable database. You'd go in either on the organization or the developer end, and put in your info.

Once you were matched on a project, though, I think it'd be really good to maybe include rudimentary tools for coordination, messaging. I bet putting up pages for review would be really great. Perhaps (although this is very ambitious) a version monitoring system of some sort.