(This question is not about programming, but about how to avoid doing any programming. Also, lots of terminology in here-- I'm assuming someone with an answer will already know what they mean.)
Background: I'm working on single sign-on in an environment with 'federated identity'. We have several products that are federation-aware (using, e.g., WS-Federation or SAML protocol, implemented with, e.g., WIF on .NET and Fedlet on Java), and they are offered to customers using a SaaS model. Many of those customers don't have their own store of usernames/passwords, so they will not run an "identity provider" themselves.
Question: Is there a product out there that
can be installed at the SaaS provider;
plays the role of an IdP/STS (i.e., identity provider in a federated enviroment) to the SaaS-provided applications;
has its own username/password store, separately for each SaaS customer ("tenant");
allows the SaaS customer to do his own user management, without requiring assistance from the SaaS provider.
(We could build this ourselves, e.g., as a custom STS on top of WIF with user admin screens, but we're trying to avoid that. It's not really our core business.)