A new standard for identity management.
If you need to maintain too many user accounts at various sites, if you are fed up with login to each site you visit (not a big deal as most sites provides 'remember me' option; still it annoying if u change machine). If the site supports openid authentication, then you can use the same openid account for that site. additionally it supports SSO.
check it out more about open id:
You can get your openid accout with: