I don't know of any that are available, but with the SSI includes it isn't hard to create one. I did a while back for a movies database site so that anytime a new movie or actor was added to the main site a new discussion thread would be created on the forum for it.
The basic PHP code was something like this:
include_once('/home/path/to.../forum/SSI.php');
require_once($sourcedir . '/Post.php');
require_once($sourcedir . '/Subs-Post.php');
$topicOptions = array(
'id' => 0, // 0 = New Topic otherwise Topic id to reply..
'board' => 22, //What board to post on.. User doesn't even need rights to view it..
'mark_as_read' => false,
);
$posterOptions = array(
'id' => (isset($ID_MEMBER) ? $ID_MEMBER : 0),
'name' => 'Add Name',
'email' => 'webmaster@yourdomain.com',
'ip' => $forummsg['IP'],
'update_post_count' => 0,
);
$msgOptions = array(
'id' => 0,
'subject' => 'Add your post title here',
'body' => 'Your post message goes here.',
);
createPost ($msgOptions,$topicOptions,$posterOptions);
If you can pull content from an rss feed or some other source and place it into PHP variables you could use the above code to insert that content into your forum and auto-populate it pretty easy.
Hope that helps.
edit: just thinking of this now it might be a great way to add content for small niche minisites. Build a forum on the site, create a number of member accounts, seed the content from multiple rss feeds related to your site niche and add some random function to the code above for randomly making the posts from those multiple member accounts you created so it doesn't look like just 1 person posting everything.
LOL looks like I've got a project for this evening now