Podcasts! Podcasts! AD, Exchange and SQL.
Well they look like overviews to me...but see if you like them!!
Active Directory Fundamentals
Migrating from Windows NT Server 4.0 to Windows Server 2003
Best Practices for designing the Active Directory Structure
New Features of Windows Server 2003 Active Directory - Feature Based
New Features of Windows Server 2003 Active Directory - Scenario Based
Understanding Group Policy - Part 1
Understanding Group Policy - Part 2
Understanding Group Policy - Part 3
SQL Server 2005 Technical Overview
Managing and Administering SQL Server 2005
Technical Overview of SQL Server 2005 Scalability Features
Upgrading to SQL Server 2005
Upgrading from Exchange Server 5.5 to Exchange Server 2003
Increasing Operational Efficiency Reduce IT Complexity