What are the best current libraries/methods to authenticate users without the use of a CMS or heavy framework?
Responses should include suggestions for anything you
I use OpenID .
But like stackoverflow I use the Google project openid-selector to do the heavy lifting.
Demo Page here.
The obvious advantages (of OpenID) are.
OpenID is a method to authenticate users based on their existing accounts on common web services such as Yahoo, Google and Flickr.
Logins to your site are based on a successful login to the remote site.
You do not need to store sensitive user information or use SSL to secure user logins.
A current PHP version of the library can be found here.