All Unified Communication End User Reference Guides
Favorite OCS Deployment guide
End User Content for UCMicrosoft Office Communicator Quick Reference
Using Communicator with Office Applications
Microsoft Office Communicator 2007 Demo
Office Communicator Overview
Top 10 Benefits of Microsoft Office Communicator
Also, some on Exchange/Outlook:Better together: do more with Microsoft Office Outlook 2007 and Exchange Server 2007
Up to Speed with Outlook 2007
Outlook Calendar Basics
Introduction to Unified Messaging
Work with Microsoft Exchange content when offline
Exchange How To Videos
http://www.microsoft.com/exchange/evaluation/demos/default.mspx