We use claims based authentication and have one application running, say www.abc.com
This application authenticates against AD via claimns provider.
We would like to deploy another web site: www.xyz.com on the same farm and establish bi-direction single sign on. In other words, if I login into www.abc.com - when I navigate to any page on www.xyz.com - I'm logged in there.
Note - since it's two different web domains - cookies won't work - we also do not want to use redirection page - it seems that if we host both apps authenticating against the same AD - there should be very easy config in SharePoint to make this happen.