Growl is a system that handles visual notification for third-party applications. Basically, whenever Adium needs to tell you something, you have a few choices (play a sound, run a script, etc.) and one of these choices is display a Growl notification. This means that Adium will let Growl decide how the notification looks, which is convenient because Growl has a lot of nice looking interfaces, and you can customize it to look however you want. It's a very nice system, and Growl can work with a lot of other applications as well. If you don't already have Growl installed, you can download it from 'http://growl.info'.

Thanks for the bug-fix arch!! I didn't think to test stuff like that. Added a note to the description.

Wow, 75 downloads already!! I didn't think very many people would want this. Thanks to those that left comments, I really appreciate the feedback :)