Outlook & MIX06
If you didn't get a chance to see it live, the MIX06 sessions are all available online now. Christin Boyd presented an excellent demo to an EBay add-in built on top of Outlook using form regions. The add-in provides a pretty rich Outlook integration that shows all of the auctions you are watching and bidding on directly in a folder in Outlook without just resorting to a folder home page.
And just incase you were wondering, no, MS employees don't really dress like that on their down time.