This plugin adds a checkbox in the post/page admin (for the admins and editors) to tell members (notification & email) that an important post has been published :
Just check the checbox at the bottom of a page/post when editing it.
(You won’t be able to post a notification if the post/page is not published; password protected or if a notification has been sent before.)
(If a notification has been sent before; the checkbox will be disabled. You can eventually re-enable it by deleting the meta key bp_admin_notifications_sent.)
Careful : I don’t have tested this plugin with a large amount of members. I suspect the mail function could not support it. Please tell me if you try !