forum within wordpress blog – how they do that?

Over at ScribeFire, I just came upon something really interesting. It looks like they’ve integrated a forum into their WordPress blog. Nice clean transition from blog to forum “look and feel”. How do they do that?! Special plug-in? Very nice indeed…

update:

A quick search brought up a couple of possibilities. Main players are RS Discuss, XDForum, WP-forum, and Simple Forum. Here’s a list from the WordPress site:

Forum plugins for WordPress