Robin W

This Plugin lets you add ranking elements to topics, replies and profiles in bbPress
These appear after the author details on each post and can show any or all of the following in ANY order
Total Topics eg ‘Topics : 78’ – you can set the wording and syntax 
Total Replies eg ‘Replies : 157’ – you can set the wording and syntax 
Total Count eg ‘Total posts : 135’ – you can set the wording and syntax 
Your name for that level – eg ‘ace contributer’ 
Some stars for that level – in the colour of your choice 
An image for that level – you can specify the size.
You can also style and add badges to users, such as ‘Key contributor’

bbp user ranking

This is awesome. Just what I was looking for. Thanks Robin.

Just what I was looking for

For bbPress - Lets you add ranking and badges to topics, replies, and profiles

dFactory

<a href="http://www.dfactory.eu/plugins/bbpress-notifications/" rel="nofollow ugc">bbPress Notifications</a> allows you to automatically send email notifications to specific users when new topics or replies are posted. It integrates seamlessly into WP, by adding new section to bbPress settings page, where you can configure your notifications.
For more information, check out plugin page at <a href="http://www.dfactory.eu/" rel="nofollow ugc">dFactory</a> or plugin <a href="http://www.dfactory.eu/support/forum/bbpress-notifications/" rel="nofollow ugc">support forum</a>.
<h4>Features include:</h4>
<ul>
<li>Send notification when New Topic is published</li>
<li>Send notification when New Reply is published</li>
<li>Specify email addresses for notifications</li>
<li>Design email templates with a number of shortcodes</li>
<li>Available shortcodes: [blogname], [reply-title], [reply-content], [reply-excerpt], [reply-url], [reply-author], [topic-title], [topic-url], [topic-author]</li>
<li>.pot file for translations included</li>
</ul>

bbPress Notifications

bbPress Notifications allows you to automatically send email notifications to specific users when new topics or replies are posted.

bbp user ranking vs bbPress Notifications