Wordpress - What is an easy way to display a front-end user registration form?

Jeff Starr wrote a great tutorial on front-end registration, login and password recovery
taking the similar approach as suggested by onetrickpony. So take this as a follow up to his answer and as another resource that might help you get it done:
http://digwp.com/2010/12/login-register-password-code/

Now you have two examples how to code this yourself and trust me - it's definitely worth doing it this (your own) way. It's not that hard and it gives you freedom, flexibility and reusability that no plugin can offer.

in case you want to handle this yourself, here's what I use:

add_action('template_redirect', 'register_a_user');
function register_a_user(){
  if(isset($_GET['do']) && $_GET['do'] == 'register'):
    $errors = array();
    if(empty($_POST['user']) || empty($_POST['email'])) $errors[] = 'provide a user and email';
    if(!empty($_POST['spam'])) $errors[] = 'gtfo spammer';

    $user_login = esc_attr($_POST['user']);
    $user_email = esc_attr($_POST['email']);
    require_once(ABSPATH.WPINC.'/registration.php');

    $sanitized_user_login = sanitize_user($user_login);
    $user_email = apply_filters('user_registration_email', $user_email);

    if(!is_email($user_email)) $errors[] = 'invalid e-mail';
    elseif(email_exists($user_email)) $errors[] = 'this email is already registered, bla bla...';

    if(empty($sanitized_user_login) || !validate_username($user_login)) $errors[] = 'invalid user name';
    elseif(username_exists($sanitized_user_login)) $errors[] = 'user name already exists';

    if(empty($errors)):
      $user_pass = wp_generate_password();
      $user_id = wp_create_user($sanitized_user_login, $user_pass, $user_email);

      if(!$user_id):
        $errors[] = 'registration failed...';
      else:
        update_user_option($user_id, 'default_password_nag', true, true);
        wp_new_user_notification($user_id, $user_pass);
      endif;
    endif;

    if(!empty($errors)) define('REGISTRATION_ERROR', serialize($errors));
    else define('REGISTERED_A_USER', $user_email);
  endif;
}

the code is almost identical to the one from the user signup page.

then add your form in your template:

<?php
  if(defined('REGISTRATION_ERROR'))
    foreach(unserialize(REGISTRATION_ERROR) as $error)
      echo "<div class=\"error\">{$error}</div>";
  // errors here, if any

  elseif(defined('REGISTERED_A_USER'))
    echo 'a email has been sent to '.REGISTERED_A_USER;
?>
<form method="post" action="<?php echo add_query_arg('do', 'register', home_url('/')); ?>">
  <label>
    User:
    <input type="text" name="user" value=""/>
  </label>

  <label>
    Email:
   <input type="text" name="email" value="" />
  </label>

  <label>
    Delete this text:
   <input type="text" name="spam" value="some_crappy_spam_protection" />
  </label>

  <input type="submit" value="register" />
</form>

you can either create a widget with this, a shortcode or just the usual page template...