PowerShell, the bits formerly known as Monad. If you're a TFS Admin, you'll be very glad figuring out how much you'll be able to do with it.
Two significant areas of PowerShell are:
- Commandlets to perform common administrative/operational tasks: Imagine a commandlet to report the currently active web requests, or the most recent X events of a given category or higher;
- Automation infrastructure: A commandlet to populate AD with a given set of users. Maybe another to take that set of users and give them a some initial permissions with TFS. Still another to validate those users have been modified as expected after using UI automation to modify them from the security/group membership dialogs in VS.
The former is more interesting because it might be a good extensibility point for those actions. If you can invoke and process output from PowerShell, you can do any of the queries/reports/actions implemented as a commandlet.
Registered users can grab the updated RC1 of PowerShell here.