Drag & Drop (functions.php code and referenced JS file below)

functions.php

///////////////////////////////////////////////////////////////////////////////////////////
// CODE TO ADD POST PER PAGE FILTER
///////////////////////////////////////////////////////////////////////////////////////////    
    add_filter( 'edit_posts_per_page', 'reorder_edit_posts_per_page', 10, 2 );
    function reorder_edit_posts_per_page( $per_page, $post_type ) {

        // CHECK USER PERMISSIONS
        if ( !current_user_can('edit_others_pages') )
            return;
        $post_type_object = get_post_type_object( $post_type );

        // ONLY APPLY TO HIERARCHICAL POST TYPE
        if ( !$post_type_object->hierarchical )
            return;

        // ADD POST PER PAGE DROP DOWN UI
        add_action( 'restrict_manage_posts', 'reorder_posts_per_page_filter' );

        // ADD SPECIAL STYLES (MOVE CURSOR & SPINNING LOADER AFTER REORDER)
        wp_enqueue_script( 'page-ordering', get_bloginfo('stylesheet_directory') . '/page-resorting.js', array('jquery-ui-sortable'), '0.8.4', true );
        add_action( 'admin_print_styles', 'reorder_admin_styles' );

        if ( isset( $_GET['spo'] ) && is_numeric( $_GET['spo'] ) && ( $_GET['spo'] == -1 || ($_GET['spo']%10) == 0 ) ) :
            global $edit_per_page, $user_ID;
            $per_page = $_GET['spo'];
            if ( $per_page == -1 )
                $per_page = 99999;
            update_user_option( $user_ID, $edit_per_page, $per_page );
        endif;
        return $per_page;
    }


    // STYLING CSS FOR THE AJAX
       function reorder_admin_styles() {
        echo '<style type="text/css">table.widefat tbody th, table.widefat tbody td { cursor: move; }</style>';
       }


    // FUNCTION TO CREATE THE NUMBER OF POSTS PER PAGE DROPDOWN UI
       function reorder_posts_per_page_filter() {
        global $per_page;       
        $spo = isset($_GET['spo']) ? (int)$_GET['spo'] : $per_page;
       ?>
        Display:<select name="spo" style="width: 100px;">
            <option<?php selected( $spo, -1 ); ?> value="-1"><?php _e('All Results'); ?></option>
            <?php for( $i=10;$i<=100;$i+=10 ) : ?>
            <option<?php selected( $spo, $i ); ?> value="<?php echo $i ?>"><?php echo $i; ?> <?php _e('Results'); ?></option>
            <?php endfor; ?>        
        </select>
       <?php
       } 



    ///////////////////////////////////////////////////////////////////////////////////////////////////////////////
    // ACTUAL AJAX REQUEST FOR SORTING PAGES 
    ///////////////////////////////////////////////////////////////////////////////////////////////////////////////

    add_action( 'wp_ajax_simple_page_ordering', 'reorder_do_page_ordering' );
    function reorder_do_page_ordering() {

        // RECHECK PERMISSIONS
        if ( !current_user_can('edit_others_pages') || !isset($_POST['id']) || empty($_POST['id']) || ( !isset($_POST['previd']) && !isset($_POST['nextid']) ) )
            die(-1);

        // IS IT A REAL POST?
        if ( !$post = get_post( $_POST['id'] ) )
            die(-1);
        $previd = isset($_POST['previd']) ? $_POST['previd'] : false;
        $nextid = isset($_POST['nextid']) ? $_POST['nextid'] : false;
        if ( $previd ) {

            // FETCH ALL THE SIBLINGS (RELATIVE ORDERING)
            $siblings = get_posts(array( 'depth' => 1, 'numberposts' => -1, 'post_type' => $post->post_type, 'post_status' => 'publish,pending,draft,future,private', 'post_parent' => $post->post_parent, 'orderby' => 'menu_order', 'order' => 'ASC', 'exclude' => $post->ID ));
            foreach( $siblings as $sibling ) :

                // BEGIN UPDATING MENU ORDERS
                if ( $sibling->ID == $previd ) {
                    $menu_order = $sibling->menu_order + 1;
                    // UPDATE THE ACTUAL MOVED POST TO 1 AFTER PREV
                    wp_update_post(array( 'ID' => $post->ID, 'menu_order' => $menu_order ));
                    continue;
                }

                // NOTHING LEFT TO DO - NUMBERS CORRECTLY PADDED
                if ( isset($menu_order) && $menu_order < $sibling->menu_order )
                    break; 

                // NEED TO UPDATE THE SIBLINGS MENU ORDER AS WELL
                if ( isset($menu_order) ) {
                    $menu_order++;
                    // UPDATE THE ACTUAL MOVED POST TO 1 AFTER PREV
                    wp_update_post(array( 'ID' => $sibling->ID, 'menu_order' => $menu_order )); 
                }       
            endforeach;
        }

        if ( !isset($menu_order) && $nextid ) {

            // FETCH ALL THE SIBLINGS (RELATIVE ORDERING)
            $siblings = get_posts(array( 'depth' => 1, 'numberposts' => -1, 'post_type' => $post->post_type, 'post_status' => 'publish,pending,draft,future,private', 'post_parent' => $post->post_parent, 'orderby' => 'menu_order', 'order' => 'DESC', 'exclude' => $post->ID ));
            foreach( $siblings as $sibling ) :

                // START UPDATING MENU ORDERS
                if ( $sibling->ID == $nextid ) {
                    $menu_order = $sibling->menu_order - 1;
                    // UPDATE THE ACTUAL MOVED POST TO 1 AFTER PREV
                    wp_update_post(array( 'ID' => $post->ID, 'menu_order' => $menu_order ));
                    continue;
                }

                // NOTHING LEFT TO DO - NUMBER ALREADY PADDED
                if ( isset($menu_order) && $menu_order > $sibling->menu_order )
                    break; 

                // NEED TO UPDATE THE SIBLING MENU ORDER
                if ( isset($menu_order) ) {
                    $menu_order--;
                    // UPDATE THE ACTUAL MOVED POST TO 1 AFTER PREV
                    wp_update_post(array( 'ID' => $sibling->ID, 'menu_order' => $menu_order )); 
                }       
            endforeach;
        }

        // FETCH ALL THE SIBLINGS WITH RELATIVE ORDERING AND IF THE MOVED POST HAS CHILDREN REFRESH THE PAGE
        $children = get_posts(array( 'depth' => 1, 'numberposts' => 1, 'post_type' => $post->post_type, 'post_status' => 'publish,pending,draft,future,private', 'post_parent' => $post->ID ));
        if ( !empty($children) )
            die('children');
        die();
    }

page-resorting.js

/////////////////////////////////////////////////////////////////////////////////////////////////////
// THIS SCRIPT APPLIES TO THE CUSTOM SCRIPT MODIFICATION ALLOWING HIERARCHICAL PAGES TO BE REORDERED
/////////////////////////////////////////////////////////////////////////////////////////////////////

// NOTE: make sure the previous code added to your functions.php file references this code correctly.

jQuery("table.widefat tbody").sortable({  
    cursor: 'move',
    axis: 'y',
    containment: 'table.widefat',
    scrollSensitivity: 40,
    helper: function(e, ui) {                   
        ui.children().each(function() { jQuery(this).width(jQuery(this).width()); });
        return ui;
    },
    start: function(event, ui) {
        if ( ! ui.item.hasClass('alternate') ) ui.item.css( 'background-color', '#ffffff' );
        ui.item.children('td, th').css('border','none');
        ui.item.css( 'outline', '1px solid #dfdfdf' );
    },
    stop: function(event, ui) {     
        ui.item.removeAttr('style');
        ui.item.children('td, th').removeAttr('style');
    },
    update: function(event, ui) {   
        if ( ui.item.hasClass('inline-editor') ) {
            jQuery("table.widefat tbody").sortable('cancel');
            alert( 'Please close the quick editor before reordering this item.' );
            return;
        }

        var postid = ui.item.find('.check-column input').val(); // THIS POST ID
        var postparent = ui.item.find('.post_parent').html();   // POST PARENT

        var prevpostid = ui.item.prev().find('.check-column input').val();
        var nextpostid = ui.item.next().find('.check-column input').val();

        // can only sort in same tree

        var prevpostparent = undefined;
        if ( prevpostid != undefined ) {
            var prevpostparent = ui.item.prev().find('.post_parent').html()
            if ( prevpostparent != postparent) prevpostid = undefined;
        }

        var nextpostparent = undefined;
        if ( nextpostid != undefined ) {
            nextpostparent = ui.item.next().find('.post_parent').html();
            if ( nextpostparent != postparent) nextpostid = undefined;
        }   

        // DISPLAY AN ALERT MESSAGE IF ANY OF THE FOLLOWING TAKES PLACE
        // IF PREVIOUS AND NEXT ARE NOT AT THE SAME TREE LEVEL OR NOT AT THE SAME TREE LEVEL AND THE PREVIOUS PAGE IS THE PARENT OF THE NEXT OR JUST MOVED BENEATH ITS OWN CHILDREN                     
        if ( ( prevpostid == undefined && nextpostid == undefined ) || ( nextpostid == undefined && nextpostparent == prevpostid ) || ( nextpostid != undefined && prevpostparent == postid ) ) {
            jQuery("table.widefat tbody").sortable('cancel');
            alert( "SORRY, THIS ACTION IS NOT POSSIBLE!\n\n>>> WHY THIS DOES NOT WORK:\nDrag-and-Drop capabilities only work for items within their current tree.\n\n>>> HERE IS HOW YOU CAN MOVE IT:\nIn order to move this item to the location you specified you simply need to use the \"Quick Edit\" link and modify the associated \"Parent\" page.\n\n>>> LOCATING THE QUICK EDIT LINK:\nOn the post you want to move, just hover over the post title and click on the \"Quick Edit\" link which appears below the title." );
            return;
        }

        // SHOW AJAX SPINNING SAVE ELEMENT
        ui.item.find('.check-column input').hide().after('<img alt="processing" src="images/wpspin_light.gif" class="waiting" style="margin-left: 6px;" />');

        // EXECUTE THE SORTING VIA AJAX
        jQuery.post( ajaxurl, { action: 'simple_page_ordering', id: postid, previd: prevpostid, nextid: nextpostid }, function(response){           
            if ( response == 'children' ) window.location.reload();
            else ui.item.find('.check-column input').show().siblings('img').remove();
        });

        // FIX CELL COLORS
        jQuery( 'table.widefat tbody tr' ).each(function(){
            var i = jQuery('table.widefat tbody tr').index(this);
            if ( i%2 == 0 ) jQuery(this).addClass('alternate');
            else jQuery(this).removeClass('alternate');
        });
    }
}).disableSelection();