One idea to save as draft

Another simple example to save a node as draft (private).

1. requires
- CCK with number.module enabled
- Content Access
- yourmodule.module with hook_nodeapi.

2. set content access to story node type as following:
view - anonymous user, authenticated user, author
edit - author
delete - author

2. add a field named 'field_is_draft' to story node type
which is a checkbox and if true it means the node is draft.

3. make yourmodule_nodeapi as folowings:

function yourmodule_nodeapi(&$node, $op, $teaser, $page) {
  switch ($op) {
    case 'submit':
      if ($node->type == 'story') {
        if ($node->field_is_draft[0]['value']) {
          //viewable only by the author
          $settings = array(
            'view' => array('author' => 'author'),
            'update' => array('author' => 'author'),
            'delete' => array('author' => 'author')
          );
          $message = 'The node is saved as drafts.';
        }
        else {
          //viewable by everyone
          $settings = array(
            'view' => array(
              'author' => 'author',
              1 => 1,
              2 => 2
            ),
            'update' => array('author' => 'author'),
            'delete' => array('author' => 'author')
          );
          $message = 'The node is published.';
        }
        // Save per-node settings.
        content_access_save_per_node_settings($node, $settings);

        drupal_set_message(t($message));
      }
      break;
    default:
      break;
  }
}