Kumbh Design Inc.

You can set meta tags like keyword, description. You can customize on each individual page/post as well.
<h3>Features</h3>
<ul>
<li>FREE Plugin.</li>
<li>One click to Install.</li>
<li>Simple and Easy to Use</li>
<li>Do not need to edit your theme’s core files.</li>
<li>Quick and supportive.</li>
</ul>

WP Simple Meta Tags

Allows you to set meta tags like keyword, description and you can customize on each individual page/post.

Philipp Speck

This plugin will give you the ability to use the <code>excerpt</code> as <code>meta description</code> for any post or page. From now you are able to control the description of your site which will be displayed on the search engine results pages. 
By activation the plugin enables the excerpt for static edit pages in admin area.
Related Links
<ul>
<li><a href="http://www.typomedia.org/wordpress/plugins/wordpress-meta-description/" title="Homepage of WordPress Meta Description" rel="nofollow ugc">Homepage</a></li>
<li><a href="https://wordpress.org/extend/plugins/wordpress-meta-description/changelog/" title="Changelog for WordPress Meta Description" rel="ugc">Changelog</a></li>
<li><a href="https://wordpress.org/extend/plugins/wordpress-meta-description/faq/" title="FAQ for WordPress Meta Description" rel="ugc">Questions</a></li>
<li><a href="http://www.google.com/support/webmasters/bin/answer.py?hl=en&answer=35264#1" title="Create good meta descriptions" rel="nofollow ugc">Information</a></li>
</ul>
Note: 
Before installing or upgrading new plugins, please backup your database first!

WordPress Meta Description

With this plugin you can control the text which will be shown as description on the search engine results pages.

WP Simple Meta Tags vs WordPress Meta Description