jacobfriedman

For instance (because people require examples.. like myself)

add_filter('the_title','add_field');

function add_field($title)
{
global $id;
if (in_category('1') && $id) {
	global $post;
	$key = "location";
	$data = get_post_meta($post->ID,$key,true);
global $wp_query;
//print_r($wp_query);

	return $title."</a><br /><div style='font-size:10px;line-height:120%;padding-top:3px'>".$data."</div><a>";

    }
else {
	return $title;	

}
}

Check out wp-includes/classes.php. Here’s something I tossed into Walker::start_el():

$mycat=$category->term_id;
			$anychildren=get_categories('child_of='.$mycat);
			if (!$anychildren) { $postquery = query_posts('cat=' . $category->term_id .'\''); 

				$endnodelist .= '<ul>';
				if ( have_posts() ) : while ( have_posts() ) : the_post();
				$endnodelist .= '<li>' . get_the_title() . '</li>';
				endwhile;
				endif;
				$endnodelist .= '</ul>';

			}

And finally

$link .= $cat_name .'</a>' . $endnodelist;.

Hope it helps – enjoy!

Cheers
Jacob