This contribution changes the login page of osCommerce to more closely resemble that of amazon.com. Rather than two parts to the page, one for returning customers and one for new customers, the new page first asks the customer for their e-mail address. It then asks if they have a password for the store, and if yes, what it is. If they say they have a password or type one in, they are logged in. If they say they do not have a password, they are taken to the Create Account page with the e-mail address filled in.
Support at http://forums.oscommerce.com/index.php?showtopic=91791