How do I add content to the dashboard in WordPress?

<?php
/*
Plugin Name: Dashboard Google Page Rank
Plugin URI: http://wordpress.org/extend/plugins/dashboard-google-pagerank/
Description: Shows your google pagerank in the wordpress dashboard
Author: Weston Deboer
Version: 1.1
Author URI: http://westondeboer.com
*/
function gpr_wp_dashboard_test() {
include('yourfile.php');


}
function gpr_wp_dashboard_setup() {
    wp_add_dashboard_widget( 'gpr_wp_dashboard_test', __( 'Google Page Rank' ),'gpr_wp_dashboard_test');
}
add_action('wp_dashboard_setup', 'gpr_wp_dashboard_setup');

?>

I have made a small modification to the above plugin. But all you should need to do is include your file which displays the data and it should show your widget in the admin dashboard.