OpenID Membership Provider is an ASP.Net Membership provider and login control that is compatible with the OpenID Authentication 2.0 implementation.
It allows you to quickly upgrade your ASP.Net 2.0 or SharePoint site to take full advantage of OpenID.
The OpenID Membership Provider can be used side by side with another ASP.Net Membersip Provider. Users can choose how the want to log in. OpenID accounts can be linked to existing accounts, users don't have to create a new one.