To Delegate Reset and Change Password to Single User or Group:
1. Right click on the OU and click Delegate Control.
2. In the delegation of control wizard, select your OU Admins group (or whatever you are delegating to), then in the next screen select "Create a custom task to delegate".
3. In the next screen, choose the radio button for "Only the following objects in the folder", the put a check mark next to User objects, then click next.
4. In the Permissions screen, put checks next to "change password", "reset password", and the "read and write account restrictions" permissions. Then click next to finish.