Find members of Active Directory Domain Group
"Active Directory Users and Computers" comes to mind.
It's dsa.msc and is available as part of the Windows Server adminpak.
http://www.microsoft.com/DownLoads/details.aspx?familyid=86B71A4F-4122-44AF-BE79-3F101E533D95&displaylang=en
Open Active Directory Users and Computers then go to the properties of the group and click on the Members tab...