Was just playing with cl-xmpp, a Jabber client for Common Lisp. Great fun, and very easy to use compared with other Jabber clients I've played with. What am I doing with it? Well, I'm planning some clever Jabber things for TwitterBuzz.
For whatever reason, the .tar.gz on the page, which is also the one linked to from CLiki and thus used by asdf-install, isn't the most recent version. If you're using a vaguely recent XML library, you'll need the most recent version (of cl-xmpp); fortunately, you can get it by CVS. CVS location is on the web page. Then, you can just put it in a .tar.gz file and use asdf-install on it, if you like.