Preprocess function per content type
The zen subtheme accomplishes this by adding this to its theme_preprocess_node function:

function foo_preprocess_node(&amp;$variables, $hook) {
  ...
    // Optionally, run node-type-specific preprocess functions, like
  // foo_preprocess_node_page() or foo_preprocess_node_story().
  $function = __FUNCTION__ . '_' . $variables['node']-&gt;type;
  if (function_exists($function)) {
    $function($variables, $hook);
  } 
  ...
}


If you have a content type called 'news', then you would be able to create a function called foo_preprocess_node_news in your template.php file.