It's still pretty much in stealth mode, and not "finished" per-se, but I've been using it for a week now and it seems stable.
The project is DJabberd. An XMPP/Jabber server written in perl that supports plugins in a way similar to mod_perl/qpsmtpd.
It's written by Brad Fitzpatrick and Artur Bergman, so you know it's going to be good, and has just been tested with 174,000 concurrent connections (epoll rocks). The intention being to roll it out to all livejournal users eventually.