Page/Posts Review

Hey guys. Does anybody know of a way to set up WP so that when a new page/post is created the system will send out an email to Multiple Users—depending on the category—to review?

For example:
If a new page is created under Category A, Users 1, 2, & 3 would receive the notification.
However, if the new page is created under Category B, Users 1, 2, 4, & 5 would receive the email.

I have around a dozen categories and about twice that many users.

Let me know if you guys have any ideas and thanks in advance.