Ashley McGlone has a great script up for merging GPOs together through powershell.
I wish I had this script five years ago. At the time I was searching for a way to combine or merge GPOs, but there simply wasn’t a way to do it. And today there still isn’t a way to do it… until POWERSHELL! Almost every environment I see (including my own former environment) has a collection of GPOs that have evolved over time and really need to be consolidated and cleaned up.
In Windows Server 2008 R2 we released a new PowerShell module for Group Policy administration. I haven’t seen much written about it, and I don’t think many people realize it is there.