For independent local cycling advocacy groups which use our CiviCRM system (currently only Cycle Aware Wellington), you can set someone up as an adminstrator so they can do mailouts and manage memberships for their local group. They won't have access to contacts outside their own local group.
To set them up as an administrator:
If they want to be able to send mailings from their own email address, you also need to add that address to the "From Email Addresses" in CiviCRM. From the CiviCRM menu, choose Administration -> CiviMail -> From Email Addresses. There you can add a new From Email Address for them to use.