Macworld Expo conference videos posted online
The presentations offered online are broken down into six tabs: Mac OS X, applications, digital photography, design, iPod and "technology." Selecting each one of these brought a similar set of subdivisions.
For example, I found a batch of interesting presentations under Mac OS X/Administration, including a case study of Google's deployment of MacBooks using the open-source Puppet system administration tools, hints on setting up Leopard Server's collaboration services, and best practices for user accounts in Mac OS X.
Many of the directory services sessions are also online under the Server tab. All of these videos look useful.
For an overview on why some companies and even IT staff are switching from PCs to Mac, check out the switcher session video in Technology/Wizardry. It was the kickoff panel for the MacIT conference.