microkid

This generates meta descriptions for your posts automatically, using the format explained on the Official Google Webmaster Central blog in <a href="http://googlewebmastercentral.blogspot.com/2007/09/improve-snippets-with-meta-description.html" title="Improve Snippets With Meta Descriptions" rel="nofollow ugc">this article</a>. It uses author, post date, categories, number of comments and, when available, tags.
<h3>Compatibility</h3>
Although this plugin is still in BETA it should work with these other plugins:
<ul>
<li>Ultimate Tag Warrior – If you are using WP 2.3+ with native tag support my plugin will use those tags, if you have a lower version and UTW installed it will use those.</li>
<li>All in One SEO Pack – Make sure you switch of the “Autogenerate descriptions” option for this plugin or you will have two meta descriptions in your page, which can’t be good!</li>
<li>TDO Mini Forms – My plugin will grab the author of the article when it’s been submitted through this plugin.</li>
</ul>

Improved Meta Description Snippets

This generates meta descriptions as advised by the Official Google Webmaster Central blog.

alexvtn

Content Snippet Manager plugin allows you to create and manage unlimited numbers of HTML and WordPress shortcodes in your WordPress content 
You will be able to choose the position and the destination of each snippet.
For example, you may need to insert an Amazon banner or a subscription newsletter shortcode at the middle or at the end of all posts, you can do it using our plugin, without being forced to edit manually each WordPress post.
Important Javascript code, conversion script or custom css codes are not allowed on the free version, they will be removed from the WordPress editor.
To insert an header, body, footer or conversion snippet, you can configure one of available shortcode. 
<a href="https://demo.themeinprogress.eu/content-snippet-manager-pro/conversion-shortcodes" rel="nofollow ugc">https://demo.themeinprogress.eu/content-snippet-manager-pro/conversion-shortcodes/</a>
Premium features.
<blockquote>
Header snippets 
 You can insert your own Javascript and CSS code on the wp_head hook.
Body snippets 
 You can insert your own Javascript and CSS code on the wp_body hook.
Footer snippets 
 You can insert your own Javascript and CSS code on the wp_footer hook.
Conversion snippets 
 You can insert your own Javascript and CSS code inside the final thank you page of WooCommerce.
Dynamic conversion values 
 The dynamic conversion values allow you to use specific parameters of a WooCommerce order inside your snippet, when a user has been redirected to the final thank you page.
Custom post type support 
 You can include a snippet inside all available custom post types available on WordPress, instead of only the WordPress posts, pages and WooCommerce products.
Custom taxonomies support 
 You can include a snippet inside all available custom taxonomies available on WordPress, instead of only the WordPress post categories, tags and WooCommerce categories.
Device selection 
 Select one or more devices where you can load the content snippet.
User Role 
 If needed, you can hide each snippet for specific user roles, like the administrator.
</blockquote>
You can get the premium version, from the following link: 
<a href="https://www.themeinprogress.com/content-snippet-manager" rel="nofollow ugc">https://www.themeinprogress.com/content-snippet-manager/</a>
<h4>Installation</h4>
Once you have installed the plugin, you just need to activate the plugin in order to enable it.
<h4>Configuration</h4>
Content Snippet Manager will add a new admin page, where you can manage all snippets.
<h3>Translators</h3>
<h4>Available Languages</h4>
<ul>
<li>English (Default)</li>
<li>Italiano</li>
</ul>

Content Snippet Manager

Content Snippet Manager plugin allows you to create and manage unlimited numbers of HTML and WordPress shortcodes in your WordPress content

Improved Meta Description Snippets vs Content Snippet Manager