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.