Windows PowerShell!!
As we all know, Windows PowerShell is a tool which made life easy for system adminstrators. PowerShell is integrated with .Net framework, and, it enables easy access to COM and WMI component which is very usefull to perform system administration tasks, it uses cmdlets to perform admistation task using which you can create your own script using PowerShell.
Recently, Microsoft has release a quick reference quide for PowerShell, download it here.