$display_admins = false;
$order_by = 'display_name'; // 'nicename', 'email', 'url', 'registered', 'display_name', or 'post_count'
$role = ''; // 'subscriber', 'contributor', 'editor', 'author' - leave blank for 'all'
$avatar_size = 32;
$hide_empty = true; // hides authors with zero posts
$last = '';

if(!empty($display_admins)) {
	$blogusers = get_users('orderby='.$order_by.'&role='.$role);
} else {
	$admins = get_users('role=administrator');
	$exclude = array();
	foreach($admins as $ad) {
		$exclude[] = $ad->ID;
	}
	$exclude = implode(',', $exclude);
	$blogusers = get_users('exclude='.$exclude.'&orderby='.$order_by.'&role='.$role);
}
$authors = array();
foreach ($blogusers as $bloguser) {
	$user = get_userdata($bloguser->ID);
	if(!empty($hide_empty)) {
		$numposts = count_user_posts($user->ID);
		if($numposts < 1) continue;
	}
	$authors[] = (array) $user;
}

echo '<ul class="contributors">';
foreach($authors as $author) {
	$current = strtolower($author['data']->display_name[0]);
	$display_name = $author['data']->display_name;
	$avatar = get_avatar($author['ID'], $avatar_size);
	$author_profile_url = get_author_posts_url($author['ID']);

	if ($last != $current) {
		echo '<a class"alphabit" name="' . strtoupper($current) . '">' . strtoupper($current) . '</a>';
			$last = $current;
	}
	echo '<li><a href="', $author_profile_url, '">', $avatar , '</a><a href="', $author_profile_url, '" class="contributor-link">', $display_name, '</a></li>';
}
echo '</ul>';