Eugen Bobrowski

Plugin provide to help search engines to indexing site correctly.
A simple plugin to manage your robots.txt. Plugin donn’t create the file or edit it. This plugin edit WordPress output of robots.txt content. And get you a easy and usable interface to manage it.
Features
<ul>
<li>Drag-n-drop robots.txt paths</li>
<li>Changing <code>blog_public</code> option form plugin settings page</li>
<li>Site map field for robots.txt</li>
<li>Robots.txt physical file checking.</li>
</ul>

Robots.txt rewrite

first review

Provide the easy managment of your robots.txt from admin side. It propose you the advanced then standard robots.txt content too.

Lukasz Jasinski

robots.txt is a file, which tell’s search engines, which parts of your site it can display publicly. 
This plugin add’s some entries to this file, to make your site safer from some attacks, keeping all your stength in seo intact ex. allowing search engine robots to harvest pictures for image search. When preparing a new site in WordPress, it’s one of the first plugins I install.

LJPL Armored robots.txt

Add some directives to your robots.txt file to keep your site safer

Robots.txt rewrite vs LJPL Armored robots.txt