MyTwitter Connect is the ultimate solution for MyBB <-> Twitter bridging, featuring smooth login and registration.
Version 2.0
Dependencies PluginLibrary, PHP cURL
Author Shade
MyTwitter Connect lets you and your users register and login with Twitter on your MyBB forum with an high quality and lightweight solution.
Existing users can link their accounts to Twitter in order to use the login functionality without having to create a fresh new account. Users and admins can also decide what informations should be imported ("synced") with their Twitter account every time they log in.
Many options are available, including an option to tweet a customizable message on the user's timeline when he registers or links his account with Twitter.
The official documentation can be found here.
MyTwitter Connect is based upon Twitter REST API 1.1 and it's free as in freedom.