GrowliChat
Speaking of Growl, make sure you check out growliChat, a little app that manages to display an alert when your buddy's status changes to online, away or idle, including the picture and username for AIM accounts in the alert. The program is windowless and dockless and best of all, it's free. The growliChat page also links to a discussion of how to use MSN in Tiger iChat. If using MSN, growliChat displays the username for MSN Jabber transport in the alert. Pretty cool little hack.
Judith would probably want me to mention that the new version of her favorite chat program, Adium X version 0.80, now natively supports Growl notification.