PHP best practices for user authentication and password security

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 think should be considered the standard for new PHP development involving user authentication.

Why are we forcing me to edit 15-year-old content?

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.

• You don't need to be a security expert.
• Users trust the big sites with their info.
• You can request things like (nickname etc) but user has to opt in.
• You don't need to worry about:
  • registration processes
  • lost/forgotten password