jammycakes

This plugin rejects outright any comments that contain either (a) BBCode 
[url=…] tags or (b) more than a predefined number of hyperlinks. As comments 
of this nature are almost exclusively spam, this should cut down drastically on 
the amount of detritus that Akismet has to deal with, making it easier to check 
for false positives in your spam queue.
<h3>Configuration</h3>
The default settings enforce a limit of two hyperlinks per comment. 
To change this, edit the number in the line just below the copyright notice 
which says:
<pre><code>define('MAX_HYPERLINKS', 2);
</code></pre>
If you set it to zero, it will not allow any hyperlinks. To allow unlimited 
hyperlinks and only block BBCode, comment out this line.
<h3>Redistribution</h3>
Copyright (c) 2007 James McKay 
http://www.jamesmckay.net/
Permission is hereby granted, free of charge, to any person obtaining a copy 
of this software and associated documentation files (the “Software”), to deal 
in the Software without restriction, including without limitation the rights 
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell 
copies of the Software, and to permit persons to whom the Software is 
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in 
all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE 
SOFTWARE.
<h3>Reporting bugs</h3>
When reporting bugs, please provide me with the following information:
<ol>
<li>Which version of Comment Timeout you are using;</li>
<li>Which version of WordPress you are using;</li>
<li>The URL of your blog;</li>
<li>Which platform (Windows/IIS/PHP or Linux/Apache/MySQL/PHP) your server 
is running, and which versions of Apache and PHP you are using, if you 
know them;</li>
<li>The steps that need to be taken to reproduce the bug;</li>
<li>If possible, any relevant information on other plugins or configuration 
options that you may think appropriate.</li>
</ol>
See the following blog entry for further guidance on troubleshooting and 
reporting problems:
http://www.jamesmckay.net/2007/04/how-to-report-issues-with-wordpress-plugins/
<h3>For more information</h3>
For more information, please visit the plugin’s home page:
http://www.jamesmckay.net/code/link-limits/
The Mercurial repository and issue tracker for this plugin are at:
http://bitbucket.org/jammycakes/link-limits/

Link Limits

Rejects comments that contain BBCode or too many hyperlinks.

skunkbad

<a href="http://blog.skunkbad.com/wordpress/the-comment-redlist-plugin" rel="nofollow ugc">Comment Redlist</a> is a WordPress plugin that blocks comment spam before it is inserted into your database.
Manage your Comment Redlist settings on the Settings > Discussion page, or on the plugin’s dedicated options page, located in the Settings menu.
For more information, check out <a href="http://blog.skunkbad.com/wordpress/the-comment-redlist-plugin" rel="nofollow ugc">http://blog.skunkbad.com/wordpress/the-comment-redlist-plugin</a>.
Features include:
<ul>
<li>Comments blocked by word, character sequence, or IP address.</li>
<li>Blocked comments can be logged for debugging or your general information.</li>
<li>Optional javascript alert informs site visitor if Comment Redlist will detect their submission as spam.</li>
<li>Optional setting provides spammer with zero feedback, instead of an error message.</li>
<li>Optional form tokens use cookies (PHP session) to confirm a legitimate post.</li>
<li>Optional setting restricts comments to US keyboard characters, or any regular expression.</li>
<li>Optional setting removes your comment form’s Website field, and blocks any comment that contains one.</li>
</ul>

Comment Redlist

Easily block obvious spam before it is inserted into your database.

Link Limits vs Comment Redlist