I know lots of people have been asking for this, but nobody seems to have done it, and people have generally been less than helpful (as well as downright abusive) when I asked for help doing it. (I'm a PHP nebwie)
SO anyway, for the mod control panel, there could be an option similar to what the admin can do to private forums- if you create a private forum and appoint a mod to it, the mod can grant access and revoke access to only his forum.
This would be great for things like company sites where you have lots of different projects, you can make the project manager a mod and let him add members to his team or whatever, there are tons of uses.