title: What's the best approach to SSO with internal AD users and external users?
body: <p>We have a web application (asp.net mvc 3) that should support SSO for internal uses via AD. We also have a large community of external users that we want to have SSO for all of our web applications. for example: external_user1 accesses webappA, webappB and webappC all with the same login. Also, domain\user1 has access to all three webapps. we plan to use WIF and ADFS 2.0.</p>
  
  <p>We don't want to have AD accounts for all of the external users so, in the past we might have tried a solution with ADFS 1.x and ADAM. however, we're on Windows Server 2008 R2 and ADFS 2.0 cannot use AD LDS (successor to ADAM) to authenticate users. </p>
  
  <p>What is the SSO approach (using microsoft products)? </p>