One of our customers shared with us their recent solution for the Communicator client TAB functionality. I love seeing this stuff because this is what helps show that the client we ship is only the beginning.
Here is Raymon's site with the information and sample code - http://voipen.blogspot.com/2007/02/office-communicator-tabs-with-ms-lcs.html
As a reminder, my linking to his info doesn't mean that I or Microsoft have tested it. This is simply a sample. I look forward to the day when we have a lot of great samples to share with folks. If you know of others, please share.