ubuntu-geek has formalized the request process for a third-party forum on UbuntuForums.org. If you’re a developer and you have a project that fits the Ubuntu mold, and you’d like to centralize its development within the Ubuntu community, this would be a place to host it.
It’s important to note that if you already have a forum, you might have to consider abandoning it. That could be a good thing or a bad thing, depending on how you look at it. It might free you up from policing a forum all the time, since there is a dedicated staff (ahem) that does that for you. And the added traffic might be a boon.
On the other hand, if you already have an established base of users and a forum with a decent stream of traffic, you might not be keen on it. Either way, it’s an idea.