Jason Stelzer just turned me on to ERC, an IRC mode for Emacs. It even just works with Windows, and comes with recent versions of Emacs (as of April 2008).

There are even easy ways to automatically start a session and connect to a channel - wrapping that up helped make it more automatic:

(defun krb-start-erc ()
  (interactive)
  (erc-open
   "irc-server-name-or-ip"
   6667
   "your-username"
   "your-full-name"
   t ;; connect
   "your-passwd")
  (erc-join-channel "datapump"))