Cat_archives_plugin

function mb_cat_archive() {
	$categories = get_categories();
  
      foreach ($categories as $category)
  
      {
   
      query_posts('cat=' . $category->cat_ID);
      echo  '<h2>',$category->cat_name , '</h2>' , '<br />';
      if (have_posts()) :
      while (have_posts()) : the_post();
?>
     <a href="<?php the_permalink(); ?>"><?php the_title() ?></a>
      <br />
<?php
       endwhile;
       endif;
    
      } 
      
     add_action('wp_head','mb_cat_archive');

?>