py_xdb_auth is a small but robust jabber-component based on twisted to authenticate jabber users against ldap. It is written for jabberd

Jabberd, short for Jabber Daemon, is the main process in which a Jabber Server (or specific Gateway or Service) runs. It functions as the distribution hub for the Jabber server and handles the logic for routing XML packets to various components within the server (and eventually to other Jabber Clients and other Jabber Servers).