OpenID should have been the next best thing on the internet. With the internet usage growing by the day, the "one password to rule them all" idea would seem the obvious choice, as nowadays people are easily finding their way to social websites (Facebook, Netlog, ...), blogs (Wordpress, Blogger, ...) and multimedia based websites - with YouTube being the most popular one.
Adding content to "the internet" has never been easier, but for each service, one would have to remember the login name and password for it. Each website has its own restrictions with it:
username or e-mail based login
password restrictions: minimum/maximum characters, caps, ...
After a while, it becomes impossible to memorize all those logins. This is where OpenID comes in: It is used to identify yourself, no matter which site you frequent. In short, this is what happens
Visit an OpenID supported website
Enter your OpenID, and you will be redirected to the OpenID provider
Enter your credentials
The OpenID provider will then redirect you to the original website, telling that you have been successfully authenticated
If you want a more detailed explanation, please visit OpenID Explained, as they did a much better job at explaining the whole OpenID process.
Sadly, it feels to me as if the majority has lost interest in OpenID. Even though it is implemented in some well known websites (Google, Yahoo, Flickr, MySpace, AOL, Blogger, ...), it looks like most people don't even know of its existence. Maybe I'm too pessimistic though, as investigations prove that the use of OpenID is still growing. I really hope those graphs will still be pointing upwards in a few years...
I am already using OpenID for a while on my own website, but there were still some problems. I have recently made the switch to LightOpenID, which has made it a lot easier to implement. If you think implementing OpenID into your website is way over your head, maybe Janrain's Engage will make the job a lot easier.
Also, I was looking for an easy way to start my own OpenID provider. Turns out, this wasn't so easy as I hoped. There are some nice programs, but they mostly lack documentation or don't support multiple OpenID accounts. Until I found "Prairie", which was developed by Barnraiser. Their software just works out of the box, which is really amazing. Sadly, the developers have stopped working on this project about two months ago, while the software is still in alpha. Nevertheless, it is working really smoothly as it is now.
Bottomline, I still support the OpenID initiative, and hope that it will keep on growing. It may not be perfect as it is now, but it still has a lot of potential, and I will be following this project closely.