set up social login for multiple drupal sites? I intend to set up multiple independent drupal installations, each of which could benefit from social logins. I like HybridAuth, but it requires me to set up multiple "applications" (one for Google, one for Github, one for Facebook etc) for each site.

Any thoughts on how to automate creating these "applications"? Or maybe a different solution? I've tried OneAll but the Drupal module seems quite buggy.
I don't think you're going to find a way to automate the creation of application accounts. Facebook, Google, et. al have to deal with enough spam as is, without them opening up a pandora's box of spam application accounts that would come from exposing an API that could create application accounts on their respective platforms. 

HybridAuth works well if you're looking to have flexible access to each social login platform (e.g. a FB app that can request multiple user permissions to the Graph API). If you're looking for just login delegation you might find more success with one the 3rd-party social login services like the LoginRadius or the Janrain modules (there might be more, those are the only ones I've heard of).