normen

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, however not much code is left of it 😉

BP Unread Posts

destroflyer

Shows a read/unread icon next to threads (Marks topic as read when the user visits it). 
A “Mark all topic as read” button on each page allows to set the topics on that page as read. 
Developed for: http://jmonkeyengine.org

bbPress Unread Posts

Displays a read/unread icon next to threads and offers a "Mark all topics as read" button for each forum page.

BP Unread Posts vs bbPress Unread Posts