This video from TechEd Australia 2011 is from one of my favourite sessions of the entire week. It covers Lync 2010 meeting features and architecture in Microsoft Lync 2010 Client and Server, for both on-premise and Microsoft Office 365 Service deployments.
The best part of this presentation for me was the demonstration of Lync functionality. Lync is one of those products that can be difficult to grasp until you see it live in action. And unlike many other products it is difficult to set up your own demo environment to see it for yourself. So the live demo in this session was a real highlight for me.