This SEO plugin is automatically generating an overview about the keyword densities of the used keywords and 2-/3-word keyphrases in the pages / posts content. 
The statistics will be updated in a specific interval while the author is writing the text in edit-post and edit-page dialog. 
These informations have informational character only – no meta information will be inserted into your blogs pages. 
You can use the meta keyword suggestion at the bottom of the statistics to copy these informations into the input fields of your favourite SEO plugin. 
Stopwords for different languages can be filtered out of the text before the keywords densities will be calculated. 
The keyword density checker tool is a branch of the <a href="http://www.keyword-statistics.net/wordpress-plugin.html" rel="nofollow ugc">keyword statistics plugin</a>. 
If you don’t need the meta stuff the keyword density checker is much faster – no code will be executed on ordinary pageviews. 
The additional code is needed in page-/post-edit mode of admins and authors only.
Features of the SEO-Tool:
<ul>
<li>Automatic calculation of the keyword density for single keywords and keyphrases (2- and 3-words) while writing the content</li>
<li>Meta keywords suggestion depending on the pages/posts content</li>
<li>Language specific stopword lists</li>
<li>Optional filter for stopwords</li>
<li>Update interval for the statistics generation can be changed and switched off</li>
<li>Generation of statistics for 2- and 3-word phrases can be deactivated</li>
<li>Definition of the default language and stopword filter status for authors</li>
<li>Prevent authors and contributors from changing the content language and stopword filter status</li>
<li>Uses nonces for plugins security</li>
</ul>
Integrated stopwords for:
<ul>
<li>Brazilian Portoguese</li>
<li>Bulgarian</li>
<li>Czech</li>
<li>Danish</li>
<li>Dutch</li>
<li>English</li>
<li>French</li>
<li>Hungarian</li>
<li>German</li>
<li>Polish</li>
<li>Slovak</li>
<li>Spanish</li>
<li>Turkish</li>
</ul>
Backend translations for:
<ul>
<li>English</li>
<li>German</li>
</ul>
Read more about this SEO plugin on <a href="http://www.keyword-statistics.net/wordpress-keyword-density-checker.html" rel="nofollow ugc">keyword density checker</a> – <a href="http://www.keyword-statistics.net/de/wordpress-keyworddichte-plugin.html" rel="nofollow ugc">german</a>

SEO-Tool – Keyword Density Checker

This SEO-Tool provides a keyword analyzer calculating the keyword density of the page/post content and generating statistics for keywords and phrases.

husani

Searches various data sources (Google Blog Search and Twitter) for posts related to your content and displays links/summaries on your page or 
inside your posts. These links and summaries can be displayed anywhere and any way you wish — below your post, in a sidebar, etc. With the 
magic animation power of jQuery, SMIRC content can be hidden until a user clicks the customizable header.
SMIRC performs related content searching (at least in this version) by creating RSS feed URLs for the various data sources. The RSS feed is 
parsed and converted into XHTML for display in your blog.
All PHP is separated into logical classes and files, and all XHTML is standards-compliant. Lists of links, authors, and summaries are built 
using standard UL and LI tags, and can be modified to fit your theme via two CSS files contained within this plugin.
SMIRC is released to the WordPress community under the GPL. Please feel free to modify as you see fit, and if you find this plugin useful, donate 
to the author. All feedback is welcome at wordpressplugins@husani.com, and you can visit the author’s websites at http://www.husani.com and 
http://www.evb.com.
UPDATE FOR v1.1: Fixed a bug with setting header text.

Social Media Integrated Related Content (SMIRC)

Like trackbacks, but not -- this plugin searches and displays content related to your CONTENT, not just posts that link to yours.

SEO-Tool – Keyword Density Checker vs Social Media Integrated Related Content (SMIRC)