Wordpress_Make Archives.php Include Custom Post Types - Archives.php only shows content of type 'post', but you can alter it to include custom post types. http://css-tricks.com/snippets/wordpress/make-archives-php-include-custom-post-types/

add_custom_types.php

//functions.php

function namespace_add_custom_types( $query ) {
  if( is_category() || is_tag() && empty( $query->query_vars['suppress_filters'] ) ) {
    $query->set( 'post_type', array(
     'post', 'your-custom-post-type-here'
		));
	  return $query;
	}
}
add_filter( 'pre_get_posts', 'namespace_add_custom_types' );