http://drupal.org/project/notify
The notify module allows users to subscribe to periodic emails which include all new or revised content and/or comments much like the daily news letters sent by some websites. Even if this feature is not configured for normal site users, it can be a useful feature for an administrator of a site to receive notification of new content submissions and comment posts. It can be extended to select specific content to go to users individually using Views module and Notify by Views.