How to change contents of a dashboard help tab

Simply paste the code below into your functions.php file.

//hook loading of new page and edit page screens
add_action('load-page-new.php','add_custom_help_page');
add_action('load-page.php','add_custom_help_page');

function add_custom_help_page() {
   //the contextual help filter
   add_filter('contextual_help','custom_page_help');
}

function custom_page_help($help) {
   //keep the existing help copy
   echo $help;
   //add some new copy
   echo "<h5>Custom Features</h5>";
   echo "<p>Content placed above the more divider will appear in column 1. Content placed below the divider will appear in column 2.</p>";
}

Thanks to WP Tuts for the tip!