Allow a single wordpress install to serve different content to different domains. This is version 0.0.0.0.1

MultiDomainContent.php

<?php
/**
 * This part resides in wp-config and is used to assign the domains
 * 
 */
if ( !defined('ABSPATH') )
	define('ABSPATH', dirname(__FILE__) . '/');

function domain_theme($domain) {
   define('WP_SITEURL', 'http://'.$domain);
   define('WP_HOME', 'http://'.$domain);
}

$domain = $_SERVER['SERVER_NAME'];
$domain = str_replace('www.', '', $domain);
if ( 
	$domain == 'domain1.com' ||	
	$domain == 'domain2.com' || 
	$domain == 'domain3.com' 
) {
	domain_theme($domain);
}


/**
 * This is a plugin used to create the domain specific content filter.
 * Please note the version number before you judge.
 * 
 * @package Author_Switcharoo
 * @author Sherman Bausch <sbausch@nerdery.com>
 * @version  0.2
 */

/*
Plugin Name: Author Switcharoo
Plugin URI: http://shermpress.com/specifically/wordpress/
Description: Filter global site content based on the site domain. There is some coding necessary: don't be afraid.
Author: Sherman Bausch <sbausch@nerdery.com>
Version: 0.2
Author URI: http://shermpress.com/
*/

function filter_content_by_site_author($query) {
	if ( is_admin() || current_user_can("administer stuff") ) {
		return;
	}
	
	$urls = array(
		'domain1.com' => 3,
		'domain2.com' => 2,
		'domain3.com' => 1
	);

	$domain = $_SERVER['SERVER_NAME'];
	if (!isset( $urls[$domain] )) {
		return;
	}

	$tag_id = $urls[$domain];

	
	// By Tag
	$query->set('tag_id', $tag_id);

	// By User
	$query->set('author_id', wp_get_current_user()->id);
	
}

add_action('pre_get_posts', 'filter_content_by_site_author');

/**
 * Switch to this
 * http://codex.wordpress.org/Plugin_API/Filter_Reference/request
 **/