I'm surprised that nobody has done anything "Web 2.0"-ish with the humble discussion forum. The basic structure of the discussion forum hasn't changed significantly since the mid nineties. And, as I showed in The Conversation Garden yesterday, it's really not the best way to organise things. 
It would be so cool to have a system with a self-organising taxonomy. How would this work? Well, all threads would have tags. Anybody who posts to the thread could add tags. The aggregate of those tags would form the thread tags.
Subforums would simply be a list of tags. So if you wanted to have a politics subforum, you'd go in to the admin panel, and ask it to have a subforum for everyone who uses the tags: politics, politician, parliament, democracy, congress, government, law etc.
You could democratise that process. Imagine if everyone could build their own hierarchical structures in a very simple markup language (I'm not talking OPML here - this is a different type of thing). So you write out your version of the forum, and when you visit the forum, it'll be laid out how you like it.
You could aggregate those. Ask people to vote on them, and then somehow synthesise the layout based on the best design.
This would destroy the need for arguments over which forums to have where. If you're bored because there's not a forum for your taste, you simply define it into existence and if that organisation makes better sense than other competing organisations, it'll stay.
The most important page of forums, and the one which is paid so little attention to, is the "View New Posts" page. It's really the 'blog' view of the forum. People building new forums should really pay attention to how people stay up-to-date with forums. On small forums, it's the View New Posts page. On larger forums, it's "Any responses to my posts?" followed by browsing a few topics of interest.
We need to rigourously redefine discussions. If someone starts a thread, it often will take a few pages until the real questions come out for discussion. So, "what's your opinion on abortion?" is really a meta-question for "when does human life begin?". Forums should react to this, automatically refactoring threads based on what's new.
We do this in USENET through thread retitling. Retitling a thread is really refactoring it because it changes the discussion. Imagine you were discussing an ongoing event - the thread would automatically be refactored based on the changing nature of the event.
Once a news article comes out, or a verdict arrives, the opinion of people changes, so the thread should change with it.
All of this works only if you use the model of the post as the most important item in the message board. Not the thread, not the subforum. The post. Only on threaded (rather than flat) discussion boards does this actually work out in practice, since you can't properly respond to unthreaded discussion.
Of course, every user should have an RSS feed. As should every forum, every thread and every post. There should also be a way of subscribing to threads in a complex manner and getting the results delivered through RSS.
If the above sounds complicated, it is. Human discussion is complicated, and our software should reflect that rather than naïvely trying to change our discussions to fit in to what Matt Wright and his followers say it should be.
