In the Exchange UM area, it is good to know an exam is now available for Office Communications Server 2007 R2 in relation to Exchange Server 2007 Unified Messaging and Active Directory. This exam, 74-404 Microsoft Office Communications Server 2007 R2 – U.C. Voice Specialization, covers the following topics:

• Architecting and designing Microsoft Unified Communications Voice Solutions;
• Administering users, clients;
• Configuring servers and components, integration (e.g. Exchange UM);
• Troubleshooting OCS 2007 R2 deployments.

You should also have experience with network infrastructure components supporting OCS 2007 R2.

Check out the prep guide here, you can register for the exam at Prometric.