WP PHPList

Instalación

Pre-requisites
Wordpress 2.x
Phplist 2.10.2 or greater. (Download at www.phplist.com)
PHP 4.x or 5.x with cURL support

Quick Start Instructions
Download plugin installation and upload phplist.php and phplist.css to your plug-ins folder, usually /wp-content/plugins
Login to wordpress administration panel and activate the plug-in (Under plug-ins). Plugin name is phplist.
Navigate to Options -> PHPList and fill in the General Settings configuration as instructed. (Optionally, you can configure the form settings as well – see detailed instructions for information)
The last step is to setup the form. If you are adding the subscriber form directly to any post or wordpress page then just add the following comment while inside the wordpress editor:

<!--phplist form-->

For more advanced users, who are comfortable editing template files, the form can also be added to any template file. For example most users like to display the subscriber form in their sidebar.php. To do this open up the template page (i.e. sidebar.php) and add the following code:

<?php
$content = apply_filters('the_content', '<!--phplist form-->');
echo $content;?> 

Detailed instructions available here