Openfire is a chat/collaboration server that you can run on your own machine.
I do some support work for a law office here in Las Vegas. They were loving the ability to have iChat in their office, but found that while using AIM there were too many personal conversations going on during work. Also, the partners were not too excited about all their case details running thru the AIM servers.
So we installed Openfire on a Mac mini in our data center and got everyone set up there. Now the office chatting is all on a private and secure server. In addition, Openfire has an awesome set of plugins for things like content filtering.
If you’d have a use for something like this, head on over to get your copy at the community’s site. (The software is released under the Open Source GPL.)
And in case you’re looking, they also have a pretty nifty cross platform chat client called Spark. (Though iChat will work with Jabber as well.)