Such a list cannot be complete. The whole point of OpenID is that identity management is NOT linked to a single or a small number of providers.
So I can give you an other identity provider: openid.basjes.nl.
This provider handles the OpenID of exactly 1 user (perhaps 2 if my wife wants one too).
The effect I do see lately is that sites want users to be able to login with a lower threshold. Many of those users already have an account that is (technically) exposed using OpenID, but these users are not aware of this fact nor do they understand what OpenID is.
So what happens is that sites (like SO) add a few 'convenience' buttons that translate (Javascript?) the site specific userid to the corresponding OpenID. But only for the 'top 5' most popular sites. For the rest they have a normal OpenID.
Just my 2ct.