SaaS/ASP Hosting and AD Integration

I am evaluating porting our Web Application to a multi-tenant
ASP/SaaS format, and one of the requirements will be to allow our
clients to integrate with their current Active Directory Domain. I've
read a little about ADAM and Federation Services, but I am trying to
find a best policies guide or something.
Has anyone done this? I'm looking for something that is easy for our
clients to set up (they won't have strong IT departments) and won't
cost us a lot of admin time either. We will need the identity
management/SSO features.

Any information or guides would be helpful. Thanks!