OpenID is a decentralized system that reduces the number of username and password combinations you have to remember for each and every web site that demands them. Instead, you need only remember a URL - like http://my.id.example.org/ - and use it to log in. Anywhere. Well, anywhere it's taken as a valid form of login - like this wiki, or comments on our blog.

For login, the site will look up the URL you provided and check there for the location of your identity provider. For sites you use frequently, your authentication is effectively done at this step. Setting up new sites may take another page of review.

You can use any URL you have control over to act as your login identity; you'll just need to modify the page at that URL to point to your identity provider. There are several free OpenID providers; a list of them can be found at the OpenID wiki.

Since the specification for OpenID is open, you may write and run your own identity provider instead of using the above services. You can also write your own consumer that understands how to execute OpenID authentication, allowing OpenID users easy access to your services.

If you're interested in reading more on OpenID, http://openid.net/ is a good place to start.

You may want to use more than one identity depending on the purpose of your business at any given site. Appalachian is a Firefox add-on that helps you keep track of your identities and where you've used them.