After reading the post at Bloglines I have a little better idea of what it is.
OpenID allows you to create an identity online and use that identity to login to any OpenID supported site. In other words, you will no longer need to create a new username and password for every single website.
It sounds too good to be true. I guess I'll have to wait and see how this idea progresses. The Bloglines team suggest checking out the OpenID Foundation. So that's what I'll do.
Gabcast! Learning #1 - OpenID
Bloglines has become an OpenID website.