Alternatives to Messaging and Notifications
A project that is similar in scope to Notifications and is actively supported for Drupal 7 is Subscriptions.

You may also want to look at some of the more lightweight notification modules. The project Notify is designed to send out notifications whenever new content of a certain content type appear (Disclosure: I am the maintainer of Notify).

There is a Notifications via e-mail comparison at Groups.Drupal.org. This gives you a good idea of what is available for Drupal 7.