Now that PowerShell cmdlets will replace the stsadm.exe used in SharePoint Server 2007, it can be a little bit difficult to get an overview of the new commands.
A newly published article on TechNet: Index of SharePoint Server 2010 Windows PowerShell cmdlets will help you get this information in a structured way.
There is also a Stsadm to Windows PowerShell mapping (SharePoint Server 2010) available to help transitioning to the new way of administrating SharePoint 2010.