Microsoft has release a Clinic about Unified Messaging, check this out:
Title: Clinic 5091: Introduction to Microsoft Exchange Server 2007 Unified Messaging
Course Type: Self-paced Course
Available Offline: Yes
Estimated Time of Completion: 2 Hours
In this online clinic, you are introduced to the new Unified Messaging features and functionalities in Exchange Server 2007. In addition, you learn how telephony and Unified Messaging can be integrated in Exchange Server 2007. This online clinic is composed of a rich multimedia experience. It is intended for IT Professionals who are interested in telephony or Unified Messaging.
Read at source: http://msexchangeteam.com/archive/2007/08/07/446611.aspx
The E-learning link: https://www.microsoftelearning.com/eLearning/courseDetail.aspx?courseId=75413