cl-xmpp
cl-xmpp is an XMPP client implementation of RFCs 3920 and 3921 which can be thought of as the basis of any Jabber-compliant client. It provides messaging, roster, contact and presence management.

Please find more information at the common-lisp.net project page.

ASDF-install package (obsolete) http://common-lisp.net/project/cl-xmpp/cl-xmpp_latest.tar.gz