gauth 6.x-1.0-rc1

Google supports the OAuth standard for API authentication. By using this module, web applications can access a user's Google Apps account without needing the user's GApps login details. The user logs into the site with their Drupal username and password. Once authenticated, they are then immediately redirected to the Google login page where they must confirm (or reject) that the website is allowed to use an authorization token to access their Google account.