ParagoServices - A SharePoint 2010 Service Application Sample
The new Service Application Architecture in SharePoint 2010 is a replacement of the Shared Service Provider (SSP) architecture known from SharePoint 2007. The framework offers greater flexibility in configuring, scaling and administrating SharePoint shared services.
The Service Application Framework (SAF) is now part of SharePoint 2010 Foundation, the old Shared Service Provider framework was part of the MOSS 2007. But best of all, custom service applications can be developed and integrated next to the standard services like Excel Services or Business Connectivity Services (BCS).
IMPORTANT: There is a special page with more details.