JabberWerx AJAX has hit the streets!
There are easy to drop in bits for one to one chat (tabbed), group chat and a library that allows you to push data updates to your page (think pushed stock or twitter updates). It’s a pretty good system to get up and running easily.
Most of us think of XMPP/Jabber as a chat protocol, and it does that very well (as anyone using GTalk can attest to); but it’s also got a very interesting place in the web 2.0 space as a real time data push channel. Using push instead of pull/poll can dramatically reduce server loads, and also gives you new data faster.1
Building libraries and building applications are two very different things. With applications you need to make functionality available to your end users. With libraries, you need to build robust and complete solutions that will be used in ways you probably haven’t thought of yet; abstraction and building small, distinct components is key. It’s a fun and different challenge.