Mark Barnes

You can add CSS to the entire website, regardless of what theme is being used, or add it to just the current theme. You can even add CSS that displays only when you are logged on – very useful when you’re playing with a new look, and it’s not quite ready for public viewing.
That’s it! There are no other options, everything is deliberately kept simple. Everything is stored in the database, so you don’t even have to worry about file permissions on your CSS files. Even better, all three styles are served in one external CSS file which is only loaded if you have actually made any tweaks – so no wasted HTTP requests.

Style Tweaker

Style Tweaker is a simple Wordpress plugin that allows you to tweak your site's CSS files to your heart's content.

Pascal Casier

Swiss knife Toolkit for bbPress. Set global options and style your forums.
Swiss knife tweaking and hacking Toolkit for bbPress. Set global options and style your forums.
Current features:
<ul>
<li>Mentions (email someone by using the @username)</li>
<li>Forum and Topic subscription management for keymasters and moderators</li>
</ul>
And also:
<ul>
<li>Close/Protect forums to new topics (only replies on current topics allowed)</li>
<li>Close/Protect profile information so non-logged-in users cannot see them</li>
<li>Use TinyMCE editor for topics and replies to add basic HTML</li>
<li>Remove or change informational messages, descriptions and breadcrumbs</li>
<li>Auto tick the ” Notify me of follow-up replies via email ” when giving a reply</li>
<li>Move the ” Subscribe ” option of a forum to the right, not directly after the breadcrums</li>
<li>Do not grey out closed topics</li>
<li>Inverse the replies order (most recent on top)</li>
<li>Do not show the table with the list of subforums when in a forum</li>
<li>Remove bbPress css stylesheet from all pages except forum pages</li>
<li>Basic System Info (for support personnel)</li>
<li>Translation ready ! https://translate.wordpress.org/projects/wp-plugins/bbp-toolkit</li>
<li>No email sending to blocked users</li>
<li>Add search on all pages</li>
<li>And more … (see changelog)</li>
</ul>
See the screenshots for all what can be done !
Consider also the following plugins:
<ul>
<li>bbP Move Topics</li>
<li>bbP API</li>
</ul>
Special thanks to Robkk for his input in the codex! 
And thanks to Viktor Szépe for his svn-updater idea.

bbPress Toolkit

It is a very usefull plugin, but it has no support!
It has also a bug and it doesn't subscribe new registered users

Usefull but with No support

Swiss knife tweaking and hacking Toolkit for bbPress. Set global options and style your forums.

Style Tweaker vs bbPress Toolkit