MB MB

This plugin makes it easy to display the featured images of your posts in mailchimp RSS newsletters.
Once activated this plugin will add the following to your sites default rss feed:
To the rss name space declarations:
<pre><code> xmlns:media="http://search.yahoo.com/mrss/"
</code></pre>
To each individual item (if it has a featured image):
<pre><code><media:content url="[url]" type="[mimetype]" medium="image" width="100%" height="auto">
 <media:description type="plain"><![CDATA[title]]></media:description>
</media:content>
</code></pre>
The featured images are not inserted directly into the content of your posts, so you have full control over where and how to present them. 
If you send out newsletters using a Mailchimp RSS based Campaign, simply place the *|RSSITEM:IMAGE|* merge-tag in your mail template where you want the featured image inserted.
This plugin contains
<ul>
<li>100% clean lightweight code.</li>
<li>0% JS</li>
<li>0% CSS</li>
<li>0% options</li>
</ul>
The plugin uses the hooks ‘rss2_ns’ and ‘rss2_item’, part of the WordPress core API. 
Tested with WP 3.7.1 and MailChimp Dec 2013
Contribute via <a href="https://github.com/mikkelbreum/MB-ImageChimp-RSS-Feed-Enhancer/" title="MB-ImageChimp-RSS-Feed-Enhancer" rel="nofollow ugc">github</a>

MB ImageChimp RSS Feed Enhancer

Adds featured images to the default RSS feed for use with MailChimps image merge-tag

Danny van Kooten

ibericode

Harish Chouhan

Adds a beautiful, customizable sign-up bar to the top or bottom of your WordPress site. This bar is guaranteed to get the attention of your visitor and 
increase your Mailchimp subscribers.
This plugin is an add-on for the <a href="https://wordpress.org/plugins/mailchimp-for-wp/" rel="ugc">Mailchimp for WordPress plugin</a>.
<h4>Features</h4>
Mailchimp Top Bar adds a simple yet beautiful & customizable opt-in bar to the top or bottom of your WordPress site.
Using this bar, people can subscribe to a Mailchimp audience of your choice.
<ul>
<li>Guaranteed to boost conversions.</li>
<li>Unobtrusive, visitors can easily dismiss the bar.</li>
<li>Easy to install & configure, just select a Mailchimp audience and you’re good to.</li>
<li>Customizable, you can edit the bar text and colors from the plugin settings.</li>
<li>The bar can be at the top or bottom of the visitor’s screen</li>
<li>Lightweight, the plugin consists of just a single 2.6 kB JavaScript file.</li>
</ul>
<h4>More information</h4>
<ul>
<li><a href="https://wordpress.org/plugins/mailchimp-for-wp/" rel="ugc">MC4WP: Mailchimp for WordPress on WordPress.org</a></li>
<li><a href="https://www.mc4wp.com/" rel="nofollow ugc">MC4WP: Mailchimp for WordPress website</a></li>
</ul>
<h4>About the author</h4>
Mailchimp Top Bar is a plugin by <a href="https:/www.ibericode.com/" rel="nofollow ugc">ibericode</a>, a company from The Netherlands that you may know from other plugins like <a href="https://www.mc4wp.com/" rel="nofollow ugc">Mailchimp for WordPress</a>, <a href="https://www.boxzillaplugin.com" rel="nofollow ugc">Boxzilla Pop-ups</a> and <a href="https://www.kokoanalytics.com/" rel="nofollow ugc">Koko Analytics</a>.

MC4WP: Mailchimp Top Bar

Adds a Mailchimp opt-in form to the top or bottom of your WordPress site.

MB ImageChimp RSS Feed Enhancer vs MC4WP: Mailchimp Top Bar