If you are just wanting to give remote desktop rights, there is a built in Windows group on Windows 2003 and 2008.
In Windows 2003 go to the control panel, then administrative tools and double click "Computer Management". Under the "System Tools"-"Local Users and Groups", select "Groups". Double-click the "Remote Desktop Users" Group, then use the "Add" button to add the desired group from your domain.
2008 is a little different, the "Local Users and Groups" is found under the "Configuration" section. Other than that, it should be the same.