Digest mail of new registrations
It would be good to have the option to turn on a digest mail that provides a list of all new registrations in the last 24 hours and some basic details such as how many posts the account has made. Include links/HTML (sorry plaintext mail users), so most people will be able to quickly click the account link to open their profile and view the statuses.
Further suggestions by others welcome. Would love to know what data in this email would make you more comfortable with open registrations on your instance.