I tried making a site specific browser for Campfire today using Fluid. It was a bit painful at first, until I got a little help from my friends out on the internet.
Step 1: Make the new fluid isntance. Grab the high-res image for Campfire from 37Signals here.
Step 2: Add *launchpad.37signals.com* to your list of allowed URLs for browsing (thanks Steve Sanderson)
Step 3: Add scripts to to do things like growl notifications when someone says your name.
Step 4: FUN