"List-Building" is still all the rage in online marketing, and having a place on your website where potential clients and customers can sign up for your email list is essential. Making sure your site visitors see this magical place to "opt-in" is critical. Some sites have it at the top of a sidebar, some have a pop-up or a sliding form like Slide In from the WPMU folks. Another option that displays the form on every page, but is not in your visitor's way is a "bar" somewhere near the header of the site, sometimes referred to as an "Opt-In Bar".
This tutorial covers adding an "Opt-in Bar" on a WordPress site using a Mailchimp as your email subscription solution. It describes how to add an Opt-in bar to collect first name and email address while subscribing someone to your Mailchimp list. You'll want to have a self-hosted WordPress site, a Mailchimp account, the Newsletter Sign-Up plugin and some CSS knowledge.
I borrowed some styling from MarieForleo.com for demonstration purposes.