Communicator and Exchange – Special considerations for deploying Communicator in an Exchange environment
In this post the Office Communicator team explains the integration resources between Office Communicator 2007 and Outlook 2007/Exchange Server 2007.
The Office Communicator team has built a rich set of integration points with both Outlook and Exchange. Communicator Presence can be found throughout Outlook (Presence is the colored bubble that appears next to a person's name).
Read more at source: http://communicatorteam.com/archive/2008/01/29/54.aspx