we have a complete IM platform developed which would easily allow you to build IM clients using AJAX, Flash, HTML, etc, Pretty much any client platform.
The platform is called BuddyStream, you can check it out at www.buddystream.com. We support over 20 IM networks ranging from AIM, ICQ, MSN, YAHOO, IRC, Jabber, Sametime, Novell, QQ, etc. we also suppot things like presencec, notifications, alerts and bots.
IM could be used in many ways with the zimbra platform, things like adding presence next to user names to tell whether they are onlineor not, adding such presence links to notes, calendars, email footers, contact lists, withing the address book, etc.
Have the ability to hold group chats instantly when there is a question by one of teh group members, be able to send back instant messages to other co-workers or friends, etc. really, the list goes on and on.
you can also check out our api here :
thank you - samer