I'm going to be a guest on MSDN geekSpeak this coming Wednesday at 2pm CST, the topic is Contextual Collaboration Using Unified Communications . We're going to discuss how to communications-enable an application by going through a couple of demos...
The Microsoft Office Communicator 2007 SDK allows you to automate a running instance of Office Communicator 2007 to integrate Communicator functionality into your applications. There are a bunch of other SDKs that the Unified Communication team puts out...