BP Unread Posts is a plugin for BuddyPress by normen that shows a label for unread forum posts. Marks topic as read when user visits the topic. A “mark all read” button on each page allows setting the topics on that page as unread.
Based on a plugin by 3sixty.
Requires WordPress Version: WP 3.0, BuddyPress 1.2.4 or higher Compatible up to: WP 3.1, BuddyPrress 1.2.6
Download and info: http://wordpress.org/extend/plugins/bp-unread-posts/