hook_node_view()

gistfile1.aw

<?php
/*
 * Implements hook_node_view()
 *
 * Adds a note to each article node
 */
function mymodule_node_view($node, $view_mode) {
  if ($node->type == 'article') {
    $node->content['mymodule_note'] = array(); 
    $node->content['mymodule_note']['#markup'] =  
    t('My Module Was Here!');
  }
}
?>