Here is a Jabber client worth taking a look at: Gush. There are a few things I like about it. First, it tries to make Jabber accessible to everyone. Second, it is an application written in Flash and Python, but packaged as a native application for Windows, Mac OS X, and Linux. Very, very cool. Unfortunately, it creates its own "desktop" in Flash, with its own UI, so I don't think it is a good choice for a Jabber client. However, it is very, very interesting to play with for a bit.