World: r3wp

Or better:

<?

$path = ".";
$dir_handle = @opendir($path) or die("Error opening $path");
echo "Directory content: <br/>";
while ($file = readdir($dir_handle))
{
if($file!="." && $file!="..")
echo "<a href='$file'>$file</a><br/>";
}
closedir($dir_handle);
?>

Or just enable Indexes in apache.

... if you have control over that ;)

most of the times, you can put that in a .htaccess file.