DotNet OpenId

This C# OpenID library adds OpenID 2.0 Provider and Relying Party support to your web site both programmatically and through convenient drop-in ASP.NET controls.

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http://code.google.com/p/dotnetopenid/

Your Gmail Account is Now An OpenID
by Erick Schonfeld

You may not know it, but you probably have an OpenID. If you have a Yahoo account, you have an OpenID. If you have a Windows Live account, you will soon have an OpenID. And today, if you have a Google e-mail account, you can also start using your Gmail address as an OpenID.

Your Gmail Account is Now An OpenID