Our regular morning project scrum was cancelled for today, as I went back to my desk, I noticed that my Office Communicator has updated my status to "In a meeting". 

I checked my team members, theirs were updated too.

It knows this because Outlook told it about my calendar!

Another thing I liked was how you can add Active Directory groups (or possibly any outlook groups) directly as contact lists.  Which saves you the problem of adding new people (and possibly removing/maintaining your list).

That's very cool integration.  Well done MS.