Mahfuzar Rahman

The MailChimp plugin allows you to quickly and easily add a signup form for your MailChimp list as a widget on your WordPress 2.8 or higher site.
Not sure what <a href="http://www.mailchimp.com/features/full_list/" rel="nofollow ugc">MailChimp</a> is or if it will be helpful? Signup up for a <a href="http://www.mailchimp.com/signup/" rel="nofollow ugc">FREE Trial Account</a> and see for yourself!
After Installation, the setup page will guide you through entering API information, selecting your List and then add the Widget to your site. The time from starting installation to have the form on your site should be less than 5 minutes – absolutely everything can be done via the WordPress Setting GUI – no file editing at all!
<h3>Developer Mode</h3>
You can enable “Devleoper Mode” by adding the following line to your <code>wp-config.php</code> file just above the “That’s all, stope editing!” line.
<pre><code>define('MAILCHIMP_DEV_MODE', true);
</code></pre>
This will enable the MailChimp List Subscribe plugin to operate without the need to connect an external MailChimp Account, and will provide a 
subscription form widget that will not actually submit anywhere.
This will allow you to style and configure the widget in non-production environments that are not publicly accessible.
For more Developer Mode customization options see the following article:
http://connect.mailchimp.com/how-to/how-to-article-configuring-developer-mode-for-the-list-subscribe-wordpress-plugin

Easy Mailchimp Optin Form

The MailChimp plugin allows you to quickly and easily add a signup form for your MailChimp list as a widget on your WordPress 2.8 or higher site.

jaromy

<h4>Sign Me Up</h4>
This plugin is a widget that adds a simple sign-up form to your WordPress site, allowing visitors to subscribe to your mailing list. It serves as a front end to <a href="http://www.phplist.com" rel="nofollow ugc">phpList</a>, the most popular open-source newsletter manager (over 1.5 million downloads according to their website). The widget connects to phpList via AJAX, which allows a visitor to subscribe without leaving your WordPress page – no refresh or redirect is necessary.
Features:
<ul>
<li>Add a simple “sign-up to our newsletter” form to your WordPress site</li>
<li>Provides a back-end connection to the powerful open-source mailing list manager, phpList </li>
<li>Maintains the consistent look, feel, and branding of your WordPress site</li>
<li>Uses AJAX – no page refresh or redirects. Status & feedback are displayed on the same page as the form</li>
<li>Minimal, elegant, simple. Seamlessly blends in with your theme by incorporating existing styling rules</li>
<li>Easy customization – change the text of each form element so it says exactly what you want</li>
<li>Widgetized – easily add it to your site via drag & drop</li>
<li>Error checking – client side validation via popular jQuery Validation library provides immediate feedback to the user and reduces erroneous data</li>
</ul>
More information
<ul>
<li><a href="http://www.jaromy.net/wordpress-plugins/sign-me-up/" rel="nofollow ugc">Sign Me Up</a></li>
</ul>

Sign Me Up

Add a simple straightforward sign-up form to your WordPress site. Integrates with phpList, the most popular open-source newsletter manager.

Easy Mailchimp Optin Form vs Sign Me Up