#3 Shoutbox

[Noxwizard]

Niels' Fully Integrated Shoutbox: http://phpbbhacks.com/download/1255
This one was used previouly, it had some missing functionality though, like editting.

This one might be worth watching:
paul999's Ajax Shoutbox
http://www.phpbb.com/community/viewtopic.php?f=16&t=503848