Campaign Monitor is another popular e-mail newsletter system you may use to keep in touch with customers outside the realm of Magento's transactional e-mails.

Firstly, you will need the subscription form code from your Campaign Monitor list: log in to your Campaign Monitor account, and navigate to the Lists & Subscribers tab. Select a subscriber list from here:

In the right-hand column of this screen, click on the Grow your audience option:

On the next screen, you will see an option for Copy/paste a form to your site:

Once you have customized the form to your liking, click on the Get the code button at the bottom of the screen:

Copy the code presented, and log in to your Magento store's administration panel. From here, navigate to CMS | Static Blocks and click on the Add New Block button at the top-right corner of your screen:

Click on the Save Block button and open your theme's local.xml file (present at /app/design/frontend/default/m18/layout/) to assign this block to the right-hand column using the following highlighted code:

<default>
  <reference name="right">
    <block type="cms/block" name="cms_campaignmonitor">
      <action method="setBlockId">
        <block_id>newsletter_campaignmonitor</block_id>
      </action>
    </block>
  </reference>
</default>

Refreshing your store once you have saved this change will display the subscription form for your Campaign Monitor account, allowing you to style it further should you wish to: