Badi Jones

Duplicate Content Cure is an extremely simple plugin that makes WordPress more Search Engine 
friendly (And therefore improving SEO). It does this by preventing search engine spiders/bots 
from accessing pages like Archives, Tags, and Categories, which tend to contain duplicated content 
from elsewhere on your site. This is achieved by adding nofollow, noindex to 
these problem pages.
Duplicate Content Cure doesn’t have a lot of features that other SEO plugins have, but 
it also is lightning fast by comparison.

Duplicate Content Cure

Duplicate content cure is a simple plugin that improves SEO by preventing search engines from indexing pages that contain duplicate content.

Free plug in by SEO Roma

The Plagiarism plugin keeps you from being penalized by Google (Panda) for inadvertent duplicate content.
The plugin searches online for phrases in your posts that may duplicate content already on the web (even in different context or on sites you don’t know).
After you save a post or page click the “Check for Duplicate Content” button. Plagiarism will show a list of duplicate phrases.
A link is provided for every problematic phrase, showing its related search results.
You can also use Plagiarism to check for websites scraping your content after it’s published. Just come back to your posts, clear the Plagiarism box results and check again for duplicate content.
<h4>Options Provided</h4>
Several search engines are supported: 
* Google Search (default) 
* Google Blog Search 
* Bing Search 
* Bing Blog Search 
* Yahoo Search
You can also list some excluded websites (e.g. your website itself), to avoid duplicates originating from sources you own (or participate in).
Public and private proxies support is available.
<h4>Credits</h4>
The plugin initial release is based on previous work of <a href="http://webwrights.com/" title="WebwRights" rel="nofollow ugc">WebwRights</a>‘s WP Plagiarism Pal plugin.
<h4>Upcoming features</h4>
<ul>
<li>Translations</li>
<li>Alerts in post/page list</li>
<li>Better option storage</li>
<li>Uninstall function</li>
<li>Restore default setting</li>
</ul>

Plagiarism

Checks your contents (posts and pages) against the web for inadvertant duplicate content before postings. Detects online copies of your older posts.

Duplicate Content Cure vs Plagiarism