Oktay Altunergil has written an article called Company-Wide Instant Messaging with Jabberd which explains some of the benefits and pitfalls of, and alternatives to, rolling out a Jabber server in the workplace and covers some of the more practical stuff like what kind of hardware you might need, how to set up encryption on your server, and how to configure Active Directory authentication.

This a pretty good article and certainly seems to cover most of the topics involved in rolling out IM at work. Well worth a read for those looking to set up a centralised, private, small-to-medium sized IM network.

Also, my (year-old) post on Moving to Jabber in the workplace is still mostly relevant too, but more focussed on the client side of things.