Set up a forum ?

MS Office Communicator is made for businesses. They seem to have changed the name though.

The changed the name into Lync? Wait, add an H and it sound hillarious.

We have a jabber server (XMPP) inhouse. So you can use whatever client.

We use Google Talk, mostly with third party desktop clients. Another place I worked we had an internal Jabber server too.

Set up a forum ?

Yeah, kinda. The tool I'm picturing is basically a cross between an email client like Outlook, an instant messenger like MSN, and a permanant, public resource like a forum, but with better thread organization, so with a littlle bit of google wave thrown in, and better searching. Also better file sharing so also a mix of DropBox or something too. Also a list of skills and contact info for each person, and possibly their current status and schedule. So Outlook calendar, or Facebook or similar thrown into the mix as well. And more.