This mod will create a split page login as well as give you the option to allow your customers to checkout without setting up an account.  It is a combination of Easy Signup and Login and Fast and Easy Checkout and also includes CSS Javascript Loader.

 Works on 1.3.8, 1.3.9, 1.5.0, 1.5.1, 1.5.3, a.5.4, a.5.5