add_action('wp_dashboard_setup', 'custom_dashboard_widgets');

function custom_dashboard_widgets(){
	//first parameter is the ID of the widget (the div holding the widget will have that ID)
	//second parameter is title (shown in the header of the widget) -> see picture bellow
	//third parameter is the function name we are calling to get the content of our widget
	wp_add_dashboard_widget('my_custom_widget_id', 'My Widget Title', 'my_custom_widget');
}

function my_custom_widget() {
	//the content of our custom widget
	echo '<p>The content of the widget goes here.</p>';
}

http://wpcanyon.com/tipsandtricks/adding-widgets-to-wordpress-admin-dashboard/

Adding widgets to wordpress admin dashboard

wordpress

PHP