Check out this absolutely excellent use of AJAX

<a href="http://www.fohguild.org/forumspy/forumspy.php" target="_blank">http://www.fohguild.org/forumspy/forumspy.php</a>

I don't believe you need an account there to see it in action. Basically that page auto-updates dynamically every time there's a post in one of the forums. There's also a great looking mouseover window that pops up at the bottom of the screen with thread preview in it.

It's hooked into every forum in the network of sites, not just the FoH site, so any time any of the uberguilds network sites gets a post, it updates that list.

(Before anyone asks, it's hand-coded by them, and they aren't sharing. I'd LOVE to have that on my site.)

Very, very slick.