In my personal opinion, forums have been a pre-decessor of blogs and all other interactive Web2 style things on the internet. With the birth and especially the growth of blogs, I believe that forums have been put in the background a bit.
But they're back with a vengeance : Switchboard is here. Switchboard is the world's first fully integrated Blog and Forum solution.

Switchboard offers a fully integrated Blog and Forum, where discussions integrate seamlessly across the blog and the forum. And I believe that that is the killer feature. Integration is the key. Try Switchboard. Free.