If you use any instant messaging system, such as ICQ or AIM, you have probably experienced the annoyance of not being able to communicate with friends who use a different IM system. And if you also use Emacs, you may have wished you could use Emacs text editing commands when composing instant messages, or that you could customize your messaging program in lisp.
Well, your annoyances are at an end! Jabber (http://www.jabber.org) is an "open source, extensible, modularized, cross platform, instant messaging system." Someone running a Jabber client can communicate with someone running any other IM system for which a transport is running on the Jabber server. And EJab is a Jabber client which runs inside Emacs, the "extensible, customizable, self-documenting real-time display editor."
EJab is not yet production quality, but if you'd like to try it out, or possibly aid in development, check out The EJab Project Page on SourceForge, from which you can access CVS, report bugs, suggest features, subscribe to mailing lists, and more.