Adium, the reigning king of 3rd party multi-network chatting on the Mac, has been updated to v1.1, but don't be fooled: even though it appears to be a minor x.1 update, there's a pretty significant list of changes here. Tabs seem to be all new, with the ability to move the tab list to any side of the chat window (top, left, right, etc.). Customizing Adium's menubar icon has also gotten a lot easier, now that it is an official xtra for which you can download new icons from AdiumXtras.com. DirectConnect over AIM - the feature that allows you to simply drag pictures into iChat windows and have them display in-line during a chat - should also work more reliably, and it is automatically initiated when needed now. Rounding up the list of major changes is a new ability to import iChat accounts, statuses and chat transcripts, helping Adium to become your central chatting hub.
Of course this isn't all, so knock yourself out with the complete list of changes if you're feeling adventurous. Otherwise, simply start up Adium to receive the auto-update notification or head over to Adiumx.com to download a fresh copy, and be sure to donate to the Adium crew (check the bottom of the page) for their fantastic work on a great chat app.
Thanks to everyone who sent this in.