Are there any tools to do change management with Active Directory / Group Policy?

We seem to be having a lot of problems related to "forgetting some mundane detail" while managing our Group Policy settings in Active Directory, so I am curious as to whether there are any well-regarded tools available for applying source control style practices to Active Directory configurations.

It seems like there should be a way to quickly and easily run a diff against a known-good configuration to figure out what setting changed (or did not replicate to a remote server) and is thus causing problems.

Take a look at Microsoft Advanced Group Policy Management which offers GPO change management. It's a pretty good tool that they bought from Policymaker a few years ago.