Payadl

BT Captcha – simple, Bilingual, Flexible, Protect Your WP Blog Against Comment Spams 
Special thanks to the developer of <a href="https://wordpress.org/extend/plugins/anti-captcha/" rel="ugc">Anti Captcha</a> Plugin

BT Captcha

BT Captcha - simple, Bilingual, Flexible, Protect Your WP Blog Against Comment Spams

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.

BT Captcha vs Robots.txt rewrite