As of today you’ll find Code Snippets for WordPress here. The first published Code Snippet can be used to disable login with user name and force login with email address. By default WordPress allows you to login using either your user name or your email address. This neat piece of code can strengthen the security of your WordPress website as long as the mailaddress assigned to your user is visible nowhere. If someone tries to login with a valid user name this will result in an invalid username error. So there’s no hint to use the email address instead of the username.
Right now this is the only code snippet available but new code snippets will be added regularly. Take a look at the WordPress Code Snippets section.