For domains administration I’am using “MU Multi-Site” plugin.
http://private.lt/demo.jpg

Basicly only small modifications is needed:

Additional function in my wpmu-functions.php:

function get_sites ($site_id = NULL) {
global $wpdb;
if (!$site_id):
return $wpdb->get_results(“SELECT * FROM $wpdb->site WHERE public = ’1′”, ARRAY_A);
else:
return $wpdb->get_row(“SELECT * FROM $wpdb->site WHERE id = $site_id”, ARRAY_A);
endif;
}

wp-signup.php:

print ‘.’;
foreach(get_sites() as $site):
print ”.$site['domain'].”;
endforeach;
print ”;

Hmm, maybe thats all..? I’m not sure :-)