You can combine Views bulk operations with your own code to make powerful actions which can be applied to several nodes at the time.
Here is some sample code to create an action:
/* describe your action(s) */
function mymodule_action_info() {
return array(
'mymodule_action_callback' => array(
'type' => 'node',
'description' => t('My action description.'),
'configurable' => FALSE,
)
);
}
function mymodule_action_callback(&$node, $context) {
/* do something with your node here */
node_save($node);
}