Some great ideas in this thread. My word of warning: beware of feature creep! Before a feature is added ask:
1) can it be done just as effectively outside of opengoo?
Chat, for instance, I question as a new feature because I think so many really good instant messaging programs exist it might be redundant to add it.
2) if not, is there already an existing project which can be accessed via some API?
3) if not, is there already an open source project which can be integrated?
Skype integration is an excellent example of #2. Why re-invent the wheel? Also, the more integrated code is, the harder it is to roll in updates. If the API integration gives all the necessary functionality, it seems like that ought to be preferred.
Of course, the question is at least as important as the answer. For instance, is "issue tracking" really necessary as a whole separate feature in the first place, or would a simple modification of the existing task module work? Is a "user forum" really necessary when we can already use notes w/ threaded comments?