Phillip.Gooch

Auto SEO is a simple way to add all your SEO header tags from a single interface. It will generate new meta tags, replacing any old ones your theme may add already, that are fully customized to target the audience you want. Don’t want to override everything? No problem, you choose what to override and on what post types to do it. Take the tedium out of SEO.
Note: because Auto SEO is designed to override existing meta tags when needed it works a bit differently than other SEO plugins and as such may not work on every theme. While it has been tested with a wide variety of different themes naturally it would be impossible to test them all. If your having trouble getting it to active on your site I’m more than willing to help, just let me know what theme your using and I’ll take a look, contact information inside the plugin.

Auto SEO

Auto SEO is a quick, simple way to add title, meta keywords, and meta descriptions to your site all at one from a single page.

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.

Auto SEO vs WordPress Meta Description