OpenID is a shared identity service, which allows Internet users to log on to many different web sites using a single digital identity, eliminating the need for a different user name and password for each site. OpenID is a decentralized, free and open standard that lets users control the amount of personal information they provide. So, with OpenID eliminates the need for multiple usernames across different websites, simplifying your online experience.
Where can I use it?
You can use your OpenID on any one of a growing number of sites (nearly ten-thousand) which support OpenID. If one of your favorite sites doesn’t support OpenID yet, ask them when they will! Here are some places you can visit to see where you can use your OpenID to log in today:
How do I get it?
Surprisingly! You may already have one. If you use any of the following services, so you already have your own OpenID: Blogger (blogname.blogspot.com), Technorati (technorati.com/people/technorati/username), WordPress.com (username.wordpress.com) or Yahoo! (openid.yahoo.com).
OpenID is still in the adoption phase and is becoming more and more popular, as large organizations like AOL, Microsoft, Sun, Novell, etc. begin to accept and provide OpenIDs. Today it is estimated that there are over 160-million OpenID enabled URIs with nearly ten-thousand sites supporting OpenID logins.