gistfile1.php

<?php

global $post;
$post_id = $post -> ID;

if (function_exists('wpco_is_category')) {
	if ($category = wpco_is_category($post_id)) {
		// then based on category ID, you can do something...
		if ($category -> id == X) {
			echo 'This is some text/html to show on the category page';
		}
	}
}

?>