I've created a control based on the ASP.NET AJAX Control Toolkit that gives a web site the ability to easily add cross browser support for CardSpace and othe Identity Selectors.
The concept comes is loosely based on dominick baier's CardSpace Control for ASP.NET, however I think that you'll find that it should be more flexible in regards to the UI abilities.
I have offered the control to the ASP.NET AJAX Control Toolkit team and they are considering its inclusion in the project.
This prototype code is attached to this blog entry.
CsAjax.zip