How to show the tagging widget in the teaser or node list view?

For future reference you could put something like this in your theme's template.php file:

/**
 * Preprocess node.
 */
function phptemplate_preprocess_node(&$vars) {
  // add CT form if teaser
  if ($vars['teaser']) {
    $vars['content'] .= community_tags_node_view($vars['node'], TRUE);
  }
}

This is where it would be nice to have more options when calling community_tags_node_view() as proposed here: #548480: Expand API to include customizable form.