Around 2 years ago I started development of Newsletter Sign-Up, my most popular WordPress plugin which has been downloaded close to 150.000 times by now.
A lot of people using this plugin were using it with Mailchimp which is why I decided to start development of a completely new plugin: Mailchimp for WordPress.
This new plugin does everything Newsletter Sign-Up does and more and the code is of a higher standard. Because the plugin only supports Mailchimp I could build features specifically built for Mailchimp. I could also utilize their API which makes the plugin blazingly fast. Configuring the plugin got a lot easier, all you need is your API key and the plugin will fetch all your list data to ease configuring the rest of the settings.
I tried to make the plugin as flexible as possible. You can build your own form HTML mark-up but the plugin tries to give you a (big) hand by providing you with a field wizard. Also, almost all plugin settings are optional.
The plugin can be downloaded from the WordPress repository here. Hope you like it, enjoy!
Update: because of the enormous popularity of the plugin, I developed a premium version: Mailchimp for WordPress Pro. It is simply awesome, over 3000 clients would say the same.