WordPress plugin that allows you to create custom sidebars from an admin page and select these sidebars in a metbox on the page editor page.
To install this plugin download a zipped folder and then upload to WordPress. Then add the following code to your template files
<?php
$sidebar = get_post_meta($post->ID, 'csb_sidebar', true);
if($sidebar == '') $sidebar = 'default';
?>
<ul>
<?php if ( !function_exists('dynamic_sidebar') || !dynamic_sidebar()) dynamic_sidebar($sidebar); ?>
</ul>