Social Login by Janrain
Bitid Authentication, extends wordpress default authentication with the bitid-protocol
Plug-in to create a membership page with basic authentication.
Renews the security keys and salts in wp-config.php on a weekly schedule.
Change WordPress login screen to dark color to make it more contrast.
Change WordPress login screen to white color to make it clearer.
Implementation of Mozilla Persona (BrowserID) for WordPress
Add membership management and secure authentication by SPIRAL® into your WordPress site.
This plugin restricts users from registering unless the username registered is a premium Minecraft username.
Change WordPress login screen to black color to make it more contrast.
Hides logo in WordPress login screen to make it clearer.
Easy secure login, use password or OTP as you need. Works with Smart Crib dongles and free apps: Google Authenticator, Pledge, DS3 OATH, AuthWay Token
Security Improvements to standard wordpress installs.
This plugin make improve the security of the administration page by blocking unauthorized access.
Integrate Central Authentication Service (CAS) with WordPress
This plugin makes it mandatory to be logged in before viewing any content.
Allows WordPress to externalize user authentication and account creation to a Shibboleth Service Provider.
RESTful Single Signon Plugin is a WordPress plugin that allows you authenticate WordPress users with a RESTful identity provider.
Google Authenticator for your WordPress blog.
This plugin protects your registered user base by preventing registration with a disposable email addresse (like the ones provided by mailinator).
WordPress Auth using Google Authenticator is a simple plugin which allows authorization with Google Authenticator tokens.
This plugin let you use the swekey authentication USB dongle to secure your login.
Synchronize your WordPress users with a htusers file for authentication outside of WordPress
Enhanced Login Security for Your WordPress blog.
Plugin allows admin to disable anonymous users browsing of selective posts, pages, feeds or complete WordPress site.
InkMemeber plugin provides you the option to protect your content and sell them to the audience once you get paid.
Provides automatic authentication against Google OAuth2 API.
Works with Active Directory Integration to take AD octet string and convert them to images which you can use in themes.
Integrating WordPress with LDAP shouldn't be difficult. Now it isn't. Simple LDAP Login provides all of the features, none of the hassles.
IndieAuth Links enable sign in with your domain name.