A simple class based on a tutorial at WP.Tuts that creates an page with metaboxes.

simple-admin-page.php

<?php
/*
Description: A simple class based on a tutorial at WP.Tuts that creates an page with metaboxes.
Author: Stephen Harris
Author URI: http://www.stephenharris.info
*/
/*  Copyright 2011 Stephen Harris (contact@stephenharris.info)

	This program is free software; you can redistribute it and/or modify
	it under the terms of the GNU General Public License as published by
	the Free Software Foundation; either version 2 of the License, or
	(at your option) any later version.

	This program is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	GNU General Public License for more details.

	You should have received a copy of the GNU General Public License
	along with this program; if not, write to the Free Software
	Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/

/**
 * If you use this class please make sure you rename it :).  
 *
 * The class takes the following arguments
 * * $hook - the hook of the 'parent' (menu top-level page).
 * * $title - the browser window title of the page
 * * $title - the page title as it appears in the menu
 * * $permissions - the capability a user requires to see the page
 * * $slug - a slug identifier for this page
 * * $body_content_cb -(optional) a callback that prints to the page, above the metaboxes. See the tutorial for more details.
 *
 * Example use
 * $my_admin page = new WPTuts_Simple_Metabox_Admin_Page('my_hook','My Admin Page','My Admin Page', 'manage_options','my-admin-page')
 *
 * Full example below the class (which adds example metaboxes too).
*/

class WPTuts_Simple_Metabox_Admin_Page
{
	var $hook;
	var $title;
	var $menu;
	var $permissions;
	var $slug;
	var $page;

	/**
	 * Constructor class for the Simple Admin Metabox
	 *@param $hook - (string) parent page hook
	 *@param $title - (string) the browser window title of the page
	 *@param $menu - (string)  the page title as it appears in the menuk
	*@param $permissions - (string) the capability a user requires to see the page
	*@param $slug - (string) a slug identifier for this page
	*@param $body_content_cb - (callback)  (optional) a callback that prints to the page, above the metaboxes. See the tutorial for more details.
	*/
	function __construct($hook, $title, $menu, $permissions, $slug, $body_content_cb='__return_true'){
		$this->hook = $hook;
		$this->title = $title;
		$this->menu = $menu;
		$this->permissions = $permissions;
		$this->slug = $slug;
		$this->body_content_cb = $body_content_cb;

		/* Add the page */
		add_action('admin_menu', array($this,'add_page'));
	}


	/**
	 * Adds the custom page.
	 * Adds callbacks to the load-* and admin_footer-* hooks
	*/
	function add_page(){

		/* Add the page */
		$this->page = add_submenu_page($this->hook,$this->title, $this->menu, $this->permissions,$this->slug,  array($this,'render_page'),10);

		/* Add callbacks for this screen only */
		add_action('load-'.$this->page,  array($this,'page_actions'),9);
		add_action('admin_footer-'.$this->page,array($this,'footer_scripts'));
	}

	/**
	 * Prints the jQuery script to initiliase the metaboxes
	 * Called on admin_footer-*
	*/
	function footer_scripts(){
		?>
		<script> postboxes.add_postbox_toggles(pagenow);</script>
		<?php
	}



	/*
	* Actions to be taken prior to page loading. This is after headers have been set.
        * call on load-$hook
	* This calls the add_meta_boxes hooks, adds screen options and enqueues the postbox.js script.   
	*/
	function page_actions(){
		do_action('add_meta_boxes_'.$this->page, null);
		do_action('add_meta_boxes', $this->page, null);

		/* User can choose between 1 or 2 columns (default 2) */
		add_screen_option('layout_columns', array('max' => 2, 'default' => 2) );

		/* Enqueue WordPress' script for handling the metaboxes */
		wp_enqueue_script('postbox'); 
	}


	/**
	 * Renders the page
	*/
	function render_page(){
		?>
		 <div class="wrap">

			<?php screen_icon(); ?>

			 <h2> <?php echo esc_html($this->title);?> </h2>

			<form name="my_form" method="post">  
				<input type="hidden" name="action" value="some-action">
				<?php wp_nonce_field( 'some-action-nonce' );

				/* Used to save closed metaboxes and their order */
				wp_nonce_field( 'meta-box-order', 'meta-box-order-nonce', false );
				wp_nonce_field( 'closedpostboxes', 'closedpostboxesnonce', false ); ?>

				<div id="poststuff">
		
					 <div id="post-body" class="metabox-holder columns-<?php echo 1 == get_current_screen()->get_columns() ? '1' : '2'; ?>"> 

						  <div id="post-body-content">
							<?php call_user_func($this->body_content_cb); ?>
						  </div>    

						  <div id="postbox-container-1" class="postbox-container">
						        <?php do_meta_boxes('','side',null); ?>
						  </div>    

						  <div id="postbox-container-2" class="postbox-container">
						        <?php do_meta_boxes('','normal',null);  ?>
						        <?php do_meta_boxes('','advanced',null); ?>
						  </div>	     					

					 </div> <!-- #post-body -->
				
				 </div> <!-- #poststuff -->

	      		  </form>			

		 </div><!-- .wrap -->
		<?php
	}

}

	/* Example Usage */

	//Create a page
	$example = new WPTuts_Simple_Metabox_Admin_Page('edit.php',__('Title','domain'),__('Menu Title','domain'), 'manage_options','example_page','sh_example_body_content');

	//Define the body content for the page (if callback is specified above)
	function sh_example_body_content(){
		?>
		<p> This class is just a simple example of a custom admin page with metaboxes. The class is intended to act as a skeleton class. You can use it to add several admin pages, but you might find that some pages require a seperate class extension.<p>

		<p> This content always sits at the top of the page<p>
	<?php
	}

	//Add some metaboxes to the page
	add_action('add_meta_boxes','sh_example_metaboxes');
	function sh_example_metaboxes(){

		add_meta_box('example1','Example 1','sh_example_metabox','posts_page_example_page','normal','high');
		add_meta_box('example2','Example 2','sh_example_metabox','posts_page_example_page','side','high');
	}

	//Define the insides of the metabox
	function sh_example_metabox(){
		?>
		<p> An example of a metabox <p>
		<?php
	}

I took this unmodified and attached it to a plugin I am working on just to see it work.

I am signed on to wp with an administrator account whose permissions have not been altered
(ie it does have 'manage_options' assigned to it). It does create the page example in the admin
menu however when you click on it I get 'You do not have sufficient permissions to access this
page.' What would cause that to happen?

Great code!

great thx, very worthwhile