Daniel Escapa lists a handy tip for OneNote 2007 users who also use Office Communicator 2007.

OneNote joins the party: Communicator and your phone have never been closer; in fact, for some, they are one and the same. Since no phone is ever far from a notepad, we integrated Communicator with Microsoft Office OneNote. If you have OneNote installed on your computer, you can launch it from any conversation; the conversation context will be automatically stamped into the note page, and the notes you take will be linked to the conversation. If you later restart this conversation, click the OneNote button to find your notes, which you can review or update. Similarly, if you open a previous conversation from the Conversation History folder in Outlook, click the OneNote button in the toolbar to open the notes for this conversation. 

Sounds like a handy productivity tip.