p_protect
p_protect is a pretty straight-forward protection script written in PHP. It allows you to protect any page you decide within a directory. When somebody enters the wrong username or password, you automatically get a notification email.
The only thing you have to do is add the following line into the PHP page you want protected : include ("./p_protect.php");
You can download the script here (rename the file to p_protect.php) or view a demo here (username is demo, password is demo).
Enjoy!