Allow drupal users to login with their email address as well

drupal_email_login.php

<?php
//"stolen" and modified from code in login toboggan

/**
 * Capture the form stubmit and check the form_id if it matches a login form, then
 * it will check it as an email using an extra validation step
 * @param array $form The current form  (I guess...)
 * @param array $form_state The state of the current form  (I guess...)
 * @param string $form_id The unique identifier for this form
 * @see hook_form_alter
 */
function my_module_form_alter(&$form, $form_state, $form_id) {
  switch ($form_id) {
    //there are two normal login forms
    case 'user_login':
    case 'user_login_block':
      // Ensure a valid validate array.
      $form['#validate'] = is_array($form['#validate']) ? $form['#validate'] : array();
      // your validation function must run first.
      array_unshift($form['#validate'],'my_module_user_login_validate');
      break;
    //ignore other stuff
    default:
      return;
      break;
  }
}

/**
 * Capture the username entered, if there is an @ symbol, it will check it against email addresses instead of the username
 * @param array $form The current form  (I guess...)
 * @param array $form_state The state of the form (I guess...)
 */
function my_module_user_login_validate($form, &$form_state) {
  if (isset($form_state['values']['name']) && strpos($form_state['values']['name'], '@') !== false) {
    if ($name = db_result(db_query("SELECT name FROM {users} WHERE LOWER(mail) = LOWER('%s')", $form_state['values']['name']))) {
      form_set_value($form['name'], $name, $form_state);
    }
  }
}