Network Quick-Switch

network-quick-switch.php

<?php
/*
Plugin Name: Network Quick-Switch
Version: 1.0
Description: Adds the ability to quickly switch between site and network admin screens.
Author: scribu
Author URI: http://scribu.net/
*/

if ( is_multisite() ) {
	add_action( 'admin_footer', 'network_quick_switch' );
	add_filter( 'admin_user_info_links', 'remove_network_link' );
}

function network_quick_switch() {
	$current_screen = get_current_screen();

	if ( is_network_admin() ) {
		$base = 'admin_url';
		$text = __( 'Site Admin' );
	} else {
		$base = 'network_admin_url';
		$text = __( 'Network Admin' );
	}

	if ( in_array( $current_screen->parent_file, array( 'plugins.php', 'themes.php', 'users.php' ) ) ) {
		$url = $base( $current_screen->parent_file );
	} else {
		$url = $base();
	}
?>
	<a id="network-quick-switch" href="<?php echo $url; ?>"><?php echo $text; ?></a>

<style type="text/css">
#network-quick-switch {
	background-color: #f1f1f1;
	border-radius: 3px;
	float: right;
	margin: 4px 8px 0 0;
	padding: 3px 8px;
}
</style>

<script type="text/javascript">
jQuery(function ($) {
	$('#user_info').after( $('#network-quick-switch') );
});
</script>
<?php
}

function remove_network_link( $links ) {
	unset( $links[10] );

	return $links;
}

Context: http://core.trac.wordpress.org/ticket/18301