Wp_social_connect is a project mainly written in PHP and JAVASCRIPT, it's free.
WordPress plugin for signup/login using social media providers
Allow visitors to your WordPress site to register and login using their existing Twitter, Facebook, Google, Windows Live, OpenID, Yahoo or wordpress.com account.
Social Connect adds register and login buttons for Twitter, Facebook, Google, Windows Live, OpenID, Yahoo and wordpress.com on the login, register and comment forms of a WordPress site.
It makes it safe and easy for new members to register with your site and existing members to login to your site.