From http://stackoverflow.com/questions/8124089/get-value-of-custom-user-field-in-drupal-7-template

get_user_profile_field.php

<?php
function THEME_preprocess_page() {
  global $user;
  $user = user_load($user->uid); // Make sure the user object is fully loaded
  $full_names = field_get_items('user', $user, 'field_full_name');
  if ($full_names) {
    $vars['full_name'] = check_plain($full_names[0]['value']);
  }
}