Fellow MVP Paul Robichaux is a great speaker (I've attended to a couple of sessions with him), a great writter and, who knows, maybe he will become a great podcaster too. Listen to his first podcast: how Exchange UM answers the phone.
"For my inaugural podcast, I thought I'd talk about how Exchange 2007 Unified Messaging servers answer the phone, and what has to happen in order for everything to go smoothly. Enjoy! (It's in AAC format only for now until I can dig up a decent MP3 converter...)"