Dmitry Polzin has created a Vista Sidebar Gadget for Office Communicator that helps better manage multiple conversation windows.

You can download it from the Windows Live Gallery here:
http://gallery.live.com/liveItemDetail.aspx?li=2701d34d-ec6a-48ec-9ce2-a3932345f3a8

As with any gadgets the window can be either docked in the sidebar or dragged out into the desktop .

The gadget’s title bar shows your current presence with the total number of active conversations (e.g. 6).

You can also Minimize All, Maximize All, and Close All conversation windows using the buttons in the upper right.  The small OC icon maximizes/minimizes the main OC application window as well.

There are a couple of configurable Options as well, for suppressing new windows and alerts and tracking elapsed time in conversations.