Index: wp-includes/registration.php
===================================================================
--- wp-includes/registration.php	(revision 12463)
+++ wp-includes/registration.php	(working copy)
@@ -311,7 +311,8 @@
 	$user_contactmethods = array(
 		'aim' => __('AIM'),
 		'yim' => __('Yahoo IM'),
-		'jabber' => __('Jabber / Google Talk')
+		'jabber' => __('Jabber / Google Talk'),
+		'twitter' => __('Twitter')
 	);
 	return apply_filters('user_contactmethods',$user_contactmethods);
 }