Exchange Team posts part 2 of "Call Answering Rules" for Exchange 2010
Exchange (and Outlook) is the conduit whereby users can access new e-mail, contacts, calendar, news (RSS), voicemail (Exchange Unified Messaging) and presence (via OCS and your Communicator client).
Exchange 2010 extends the unified messaging functionality by offering the end user more control over call answering, this is achieved by adding a free/busy aware rule based system. In essence you (the user) have the capability to setup your own “follow-me” service, not too dissimiliar from Google Voice.
In a recent blog post this functionality is looked at in greater detail.