Yes! In additional to an official WordPress plugin, if you're using WordPress, Drupal, Prestashop or Magento, there are third-party plugins/modules that can be installed to route your site's mail through Mandrill.

WordPress

The official WordPress plugin for Mandrill is wpMandrill. It's designed to handle all of the emails generated by WordPress automatically, and sends through the Mandrill API.  

If you're not able to use wpMandrill for some reason, or if you prefer to send via SMTP, there are a number of WordPress plugins for handling email via SMTP and, in theory, any of them should work. For example, you could use the WP Mail SMTP plugin with the below settings. If you're using a different plugin, the below can help you adapt the settings for the one you're using. NOTE: you only need to use wpMandrill or one of the SMTP plugins, but not both.

Magento

A third-party plugin is available from ebizmarts to sync your Mailchimp marketing lists with Magento, and now integrate your Mandrill account for Magento's transactional needs, such as order status emails: Ebizmarts MageMonkey Mailchimp plugin.

Drupal

A third-party Mandrill module developed to work with the MailChimp module; features the ability to send all site emails through Mandrill and a reporting dashboard: http://drupal.org/project/mandrill

Prestashop

Use this third-party add-on to send all your Prestashop emails through Mandrill: http://addons.prestashop.com/en/front-office-features/5239-mandrill.html

Joomla!

A third-party extension that allows your Joomla! installation to send emails through Mandrill: http://extensions.joomla.org/extensions/content-sharing/mailing-a-d...

SPIP

A third-party plugin, Mailshot, offers SMTP or Mandrill integration.

Please note that third-party plugins are not created or maintained by Mandrill. They are listed for your convenience only, and we can't guarantee these services or products.