WordPress.org

** Use of this plugin is not recommended in versions of BuddyPress 1.2 and higher. Please consider using BuddyPress Group Activity Notifications instead: http://wordpress.org/extend/plugins/buddypress-group-activity-stream-subscription/. A conversion script for converting subscription data from this plugin to that one is coming soon **

Features: Users can subscribe to individual discussion topics from within BuddyPress; Users can subscribe to discussions on a group-by-group basis; Users are automatically unsubscribed from a group's discussions when they leave the group; Administrators can subscribe all users to the appropriate forums with a single click (potentially handy for first-time setup); Administrators can toggle whether email notification is turned on by default; Administrators can toggle whether posters receive notification of their own posts.

Developed for the CUNY Academic Commons. Visit http://commons.gc.cuny.edu to learn more about this neat project.