Globalization, specialization, and outsourcing require people to work in more collaborative ways than ever. This trend requires a matching change in the tools that information workers use to gain insight, collaborate, make decisions, and take action. Today, most business applications are effective at automating transactions, but they do not enable rich collaboration across functional boundaries. This usually leads information workers to use personal productivity tools to perform the complex interactions required to conduct business. However, this in turn leads to a loss in productivity, as users are forced to cross from one set of tools to another, often manually transporting the data through means such as cut-and-paste operations. These gaps between different business applications and productivity tools must be bridged for information workers in a way that is seamless, synchronized, and secure.

Check out this msdn article to find out about the benefits, architecture and how Office and Sharepoint easily support building components for assembling new applications.

The next step is definitely the OBA Composition Reference Toolkit.

The OBA Composition Reference Toolkit brings to surface the underlying composition capabilities of the 2007 Microsoft Office system. It integrates seamlessly with the Microsoft Office 2007 System to enable a prescriptive application composition experience for Information Workers to build and deploy Office Business Applications (OBAs) using semantically related OBA Components like Workflows, SharePoint document libraries and lists, SharePoint Pages, Web Parts, VSTO Office Client Add-ins, BI Reports, BI Dashboards etc. The toolkit comprises an OBA Composition Server and an OBA Composer. The composer allows to use a visual designer to assemble applications.

Check out this introduction on channel9

You can find the demo here http://www.wssdemo.com/redir.aspx?ID=1552  and more info on http://msdn2.microsoft.com/en-us/architecture/cc196391.aspx