Jake Spurlock

<?php
/*
Plugin Name: Show Category Children
Plugin URI: http://jakespurlock.com
Description: Widget that only shows child categories while in the category view.
Version: 0.5
Author: Jake Spurlock
Author URI: http://jakespurlock.com
*/
?>

<?php
error_reporting(E_ALL);
add_action("widgets_init", array('Widget_name', 'register'));
class Widget_name {
  function control(){
    echo 'Used to display only the child categories while browsing category archives';
  }
  function widget($args){
    echo $args['before_widget'];
    $myCat = single_cat_title('', false);
    echo $args['before_title'] . 'More ' . $myCat . $args['after_title']; ?>

    <ul>
        <?php $newmyCat = get_cat_ID( $myCat ); ?>
        <?php wp_list_categories('title_li&child_of=' . $newmyCat); ?>
    </ul>

   <?php echo $args['after_widget'];
  }
  function register(){
    register_sidebar_widget('Child Categories', array('Widget_name', 'widget'));
    register_widget_control('Child Categories', array('Widget_name', 'control'));
  }
}

?>