I would highly recommened watching this webcast series by Harold Wong, Micrsosoft on Exchange Server 2007. He starts from the basics, lays down a solid foundation and builds on some of the advanced topics and techniques. I think its worth watching If you are looking to upgrade your current Exchange 2000 or 2003 organization or moving from a Notes environment.
“Learn how you can use the new advanced management tools in the next generation of Exchange to save time. Tune in and see how to install and manage Microsoft Exchange Server 2007 with the Exchange Management Console. Our Exchange experts help you explore the features of Microsoft Exchange Server 2007, such as increased security, unified messaging, performance improvements, and ease of deployment.”