One of the big hassles for any organization with diverse applications and systems is user authentication. I know in my own situation I have somewhere between 6 and 10 different passwords that I have to remember. Microsoft is trying to address the situation with their Active Directory Federation Services (ADFS). Here's a description from an ADFS overview document found on the Microsoft downloads site:

"Federated identity management is a standards-based technology and information technology process that enables distributed identification, authentication, and authorization across organizational and platform boundaries. Federated systems need to interoperate across organizational boundaries and connect processes utilizing different technologies, identity storage, security approaches, and programming models. Within a federated system, an organization needs a standardized and secure way of expressing not only the services it makes available to trusted partners and customers but also the policies by which it runs its business, such as which other organizations and users it trusts, what types of credentials and requests it accepts, and its privacy policies."

There's also an ADFS step-by-step guide on the same site.

Check it out!