What is the recommended read if someone like to be first introduced to OpenID and later go more deeply into details to be prepared for implementation of OpenID based single sign-on?
Pointers to some introduction articles for start, then to more thorough documentation and advices are welcome.
https://rpxnow.com/ about the implementation of not only openID but openID with selector including Yahoo, Google, Facebook and AOL.
http://framework.zend.com/manual/en/zend.openid.html about how the newest version of Zend Framework (PHP) implements openID
One problematic aspects of openID at the moment is the lack of internationalisation in general. Most services, providers, etc. are still US centered. Europe hasn't discovered it yet, it seems.
Very good guide for openID-enabling your site: OpenID recipe.
Tells you from very basics what you need to make your site openID consumer, ie. enabling people to log in to your site using openID.
The concept of OpenID is excellent. As this concept is very new and not many people are aware about it. http://www.ekoob.com/10-cool-sites-to-get-your-own-openid-4058/ people can read this article to get a clear idea about OpenID and resources where they can get an OpenID for Free.