I refactored quite a bit of the user.module:

$ diffstat user.patch
database/database.mysql |    4
database/database.pgsql |    2
database/updates.inc    |   10 -
modules/block.module    |   20 +-
modules/locale.module   |    9
modules/profile.module  |  108 +++++++----
modules/system.module   |    8
modules/user.module     |  456 +++++++++++++++++++-----------------------------
8 files changed, 289 insertions(+), 328 deletions(-)

More functionality, less code.  Here is a list of the changes:

- Some user API changes:
   + When $type is 'form', you have to return an associative array of groups.  In turn, each group is an array with a 'title', 'data' and 'weight'.
   + A new $type has been added, namely 'categories'.  User settings can be organized in categories.  Categories can be sorted, as can the groups within a category.  (Ordering 'categories' is somewhat broken due to a bug in the menu system.)

- The 'my account > edit' page will use subtabs for each 'category'.  Read: you can break down the account settings into multiple subpages.

- Profile module improvements:
   + Added support for private fields to the profile module!
   + Improved workflow of profile administration pages.
   + Improved the form descriptions.

- Code improvements:
   + Unified user_edit() and user_admin_edit().
   + Unified and cleaned up the validation code.  Fixed some validation glitches too.

1 files changed, 6 insertions, 3 deletions

diff --git a/modules/locale/locale.module b/modules/locale/locale.module
index d5a3a0f13..48e2ae528 100644
--- a/modules/locale/locale.module
+++ b/modules/locale/locale.module
@@ -92,10 +92,13 @@ function locale_menu() {
 /**
  * Implementation of hook_user(). Allows each user to select an interface language.
  */
-function locale_user($type, &$edit, &$user) {
+function locale_user($type, &$edit, &$user, $category = NULL) {
   global $languages;
-  if ($type == 'form' && count($languages) > 1) {
-    return array(t('Locale settings') => form_radios(t('Language'), 'language', $user->language, $languages, t('Selecting a different language will change the language of the site.')));
+  if ($type == 'form' && count($languages) > 1 && $category == 'account') {
+    return array(array(
+      'title' => t('Locale settings'),
+      'data' => form_radios(t('Language'), 'language', $user->language, $languages, t('Selecting a different language will change the language of the site.')),
+      'weight' => 2));
   }
 }