<?php
  $post = $wp_query->post;
  if (in_category('news')) {
      include(TEMPLATEPATH.'/single-news.php');
  }
  elseif (in_category('suppliers')) {
      include(TEMPLATEPATH.'/single-suppliers.php');
  }
  elseif (in_category('people')) {
      include(TEMPLATEPATH.'/single-people.php');
  }
  else {
      include(TEMPLATEPATH.'/single-product.php');
  }
?>