Wordpress edit page metaboxes reshuffler: moves 'author' and 'revisions' boxes to the sidebar, and places the excerpt above the editor. Excerpt hint text is configurable.

adminboxshuffle.class.php

<?php

add_action('add_meta_boxes', array('AdminBoxShuffle', 'repositionDefaultMetaboxes'), 0);

class AdminBoxShuffle
{
	const EXCERPT_HINTTEXT = 'This excerpt is shown at the top of your posts and will form the preview text on gateway pages.';

	/**
	 * Reposition default metaboxes
	 */
	public static function repositionDefaultMetaboxes()
	{
		global $_wp_post_type_features;

		$shownPT = get_post_type();

		// put author & revisions to the side
		if (post_type_supports($shownPT, 'author')) {
			remove_meta_box( 'authordiv', $allposttypes, 'side' );
			add_meta_box( 'authordiv', 'Author', 'post_author_meta_box', $allposttypes, 'side', 'default' );
		}
		if (post_type_supports($shownPT, 'revisions')) {
			remove_meta_box( 'revisionsdiv', $allposttypes, 'side' );
			add_meta_box( 'revisionsdiv', 'Revisions', 'post_revisions_meta_box', $allposttypes, 'side', 'default' );
		}

		// replace excerpt with our own metabox including custom hint text
		if (post_type_supports($shownPT, 'excerpt')) {
			remove_meta_box( 'postexcerpt', $allposttypes, 'normal' );
			add_meta_box( 'postexcerpt', 'Excerpt', array(get_class(), 'doExcerptMetabox'), $allposttypes, 'normal', 'high' );
		}

		// pop out the editor box and re-add it as a "real" metabox so priority is taken into account
		if (post_type_supports($shownPT, 'editor')) {
			unset($_wp_post_type_features[$shownPT]['editor']);
			add_meta_box(
				'postdivrich',
				__('Content'),
				array(get_class(), 'doContentMetabox'),
				$shownPT, 'normal', 'high'
			);
		}
	}

	public static function doExcerptMetabox($post)
	{
		?>
		<label class="screen-reader-text" for="excerpt"><?php _e('Excerpt') ?></label><textarea rows="1" cols="40" name="excerpt" id="excerpt"><?php echo $post->post_excerpt; // textarea_escaped ?></textarea>
		<p><?php _e(self::EXCERPT_HINTTEXT); ?></p>
		<?php
	}

	public static function doContentMetabox($post)
	{
		// ensure the edit box is white like the default one
		?>
		<style type="text/css">
			#content_ifr { background: white; }
		</style>
			<?php
			// markup taken from wp-admin/edit-form-advanced.php
			?>
		<div id="postdivrich" class="postarea">

		<?php wp_editor($post->post_content, 'content', array('dfw' => true, 'tabfocus_elements' => 'sample-permalink,post-preview', 'editor_height' => 360) ); ?>

		<table id="post-status-info" cellspacing="0"><tbody><tr>
			<td id="wp-word-count"><?php printf( __( 'Word count: %s' ), '<span class="word-count">0</span>' ); ?></td>
			<td class="autosave-info">
			<span class="autosave-message">&nbsp;</span>
		<?php
			if ( 'auto-draft' != $post->post_status ) {
				echo '<span id="last-edit">';
				if ( $last_id = get_post_meta($post_ID, '_edit_last', true) ) {
					$last_user = get_userdata($last_id);
					printf(__('Last edited by %1$s on %2$s at %3$s'), esc_html( $last_user->display_name ), mysql2date(get_option('date_format'), $post->post_modified), mysql2date(get_option('time_format'), $post->post_modified));
				} else {
					printf(__('Last edited on %1$s at %2$s'), mysql2date(get_option('date_format'), $post->post_modified), mysql2date(get_option('time_format'), $post->post_modified));
				}
				echo '</span>';
			} ?>
			</td>
		</tr></tbody></table>

		</div>
		<?php
	}
}

Undefined variable: allposttypes --> add:
$allposttypes = get_post_types();