There seems to be several different widgets for providing easer registration and login. I'm curious how they work and what the difference between them are? For example, there is the OpenID selector, Loginza, and Janrain.
Connector and OAuth Connector are modules that like Janrain can connect to accounts other than OpenID, through OAuth or other methods that people write extensions for (existed an connector for the old Facebook API).
They do mostly what Janrain do - but they do it natively in Drupal so you don't get any crippled access to any API:s and you fully control the code and can patch it any way you like.
They are currently alpha, but no that the OAuth module has been ported to Drupal 7 I can probably start porting them there and continue development on it.
The first and the last link you provided takes to the same project page.
The OpenID Selector module replaces the OpenID login form provided by openid.module (an optional Drupal core module) with the same OpenID selector used, for example, on Stack Exchange sites. Though additional modules, it integrates with login provided by:
- Windows Live ID
The Loginza module replaces the Drupal core module for OpenID, as it implement OpenID authentication, and it allows to authenticate users using the login provided by the following sites/services:
- Google Account
The other difference between the modules is that the Lorenza module is for Drupal 7, while the OpenID Selector module has versions for Drupal 6 and 7.