BuddyPress.org

This plugin might also be worth a look?

http://epicalex.com/new-user-email-set-up/

I originally used this to get round a problem of needing to manually add some new users to the system but didn’t want emails/activations being sent out immediately. It provides two very customizable sections one sent to admin one to new user, I simply swapped it round so that admin received the sign up email to a specially set up email account and the user got sent a “changes are afoot you will receive your login details shortly” type message, worked quite effectively.