OpenID
Definition
OpenID is probably the most popular light-weight digital identity system.
“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.”(OpenID (Wikipedia, retrieved 19:27, 21 August 2008 (UTC))
The system
An OpenID is in the form of a URL. This URL can be the domain name of your own website, or the URL of an OpenID Identity Provider. When you log in with an OpenID, you have to log in to the Identity Provider for validation.
Using OpenID-enabled sites, web users do not need to remember traditional items of identity such as username and password. Instead, they only need to be registered with any OpenID "identity provider" (IdP). Since OpenID is decentralized, any website can use OpenID as a way for users to sign in; OpenID does not require a centralized authority to confirm a user's digital identity.
(OpenID (Wikipedia, retrieved 19:27, 21 August 2008 (UTC))How to get an OpenID
Bascially you either get an account with some web sites and services that already provide OpenIDs, e.g. Blogger, Yahoo or Flicker or there exist providers that just provide the ID.
Make your own for your organization or students is another option.
In education
Since all sorts of web 2.0 and social software applications are increasingly popular in education (see the list of web 2.0 applications), students have a real problem managing their logins.
It therefore is good a idea to help them take an "openID" and have them use it when the service supports it. OpenID directories list an ever increasing amount of OpenID enabled web sites:
Also, some applications already implicitly provide users with an OpenID, e.g. Blogger, Yahoo or Flicker.