The update_form_enhancement module enhances update.php user interface by separating modules that are up to date from those that are not.
It uses standard form_alter hook to alter the form that is displayed on second step of update.php script to select modules that need to be updated.
Note about Drupal 7 and beyond: An equivalent feature implemented by this module is already in core, so the life time of this project dies with Drupal 6.