extension.driver.php

<?php
// file extensions/resave_entries/extension.driver.php

class extension_resave_entries extends Extension
{
	public function about()
	{
		return array(
			'name' => 'Resave entries',
			'version' => '0.1',
			'release-date' => '2011-06-03',
			'author' => array(
				'name' => 'Marco Sampellegrini',
				'email' => 'm@rcosa.mp'
			)
		);
	}
	
	public function getSubscribedDelegates()
	{
		return array(
			array(
				'page' => '/system/preferences/',
				'delegate' => 'AddCustomPreferenceFieldsets',
				'callback' => 'AddCustomPreferenceFieldsets',
			)
		);
	}

	public function AddCustomPreferenceFieldsets($context)
	{
		if (isset($_POST['action']['resave']))
		{
			$id = $_POST['resave-section'];
			require_once TOOLKIT. '/class.entrymanager.php';
			$engine = Symphony::Engine();
			

			$em = new EntryManager($engine);
			$sm = new SectionManager($engine);
			$fm = new FieldManager($engine);
			$ex = new ExtensionManager($engine);

			$entries = $em->fetch($entry_id = null, $id);
			$fields  = $fm->fetch($field_id = null, $id);
			$section = $sm->fetch($id);
			
			if (!empty($entries)) $entries[0]->checkPostData(array());

			foreach ($entries as $e)
			{
				$e->commit();
				$ex->notifyMembers('EntryPostEdit', '/publish/edit/', array('section' => $section, 'entry' => $e, 'fields' => $fields));
			}
			
			Administration::instance()->Page->pageAlert(__('Entries resaved succesfully.'), Alert::SUCCESS);
		}
		
		$group = new XMLElement('fieldset');
		$group->setAttribute('class', 'settings');
		$group->appendChild(new XMLElement('legend', __('Resave entries'))); 
		
		$span = new XMLElement('span', NULL, array('class' => 'frame'));
		
		require_once TOOLKIT. '/class.sectionmanager.php';
		$sm = new SectionManager(Symphony::Engine());
		$sections = $sm->fetch();

		$options = array();
		foreach ($sections as $s)
		{
			$options[] = array(
				$s->get('id'), false, $s->get('name')
			);
		}
		
		$select = Widget::Select('resave-section', $options);
		$span->appendChild($select);
		$span->appendChild(new XMLElement('button', __('Resave Entries'), array_merge(array('name' => 'action[resave]', 'type' => 'submit'))));

		$group->appendChild($span);
		$context['wrapper']->appendChild($group);
	}
}

Awesome Marco! This will complement so many other extensions, including one I'm working on :-)