Looking into wordpress.org I saw that you will find several plug ins for openID and aAuth. I do not really obtain a feel from stars and explanations what are best and popular (have been in existence for a while and hopefully is going to be around for extended).
Perhaps you have used them? That you recommend?
While you stated there are many options available but my preferred the first is: http://wordpress.org/extend/plugins/social-connect/
It adds support for facebook, twitter, google, wordpress.com and much more.
It labored like no bodies business for me personally. Hope it will help :)