The world of WordPress is filled with too many addons for Mailchimp. For us, The problem was most of them had too many things that we did not need. All we needed was a very simple, mailchimp subscription form with slide in/slideout box.
After spending 1-1.5 hours on testing the existing plugins, we decided it is not worth spending time on searching. It will take less time to write the plugin than to keep searching.
That's how our Social Subscribe Box Mailchimp addon for WordPress originated(around 6 months ago). You can see it in action on this site. It is very simple and works great for us. A few weeks ago, One of our members( Thank you Sujee) asked us for the plugin that we are using on BuddyDev and we decided to opensource it.
If you are looking for a simple, fun filled experience with Mailchip subscription, Give a try to the plugin. You can even show your social profile links on the plugin.
WordPress.org Page:- http://wordpress.org/plugins/social-subscribe-box/
BuddyDev Plugin Page:- http://buddydev.com/plugins/social-subscribe-box/