Worth a read...
This paper is divided into two main sections. The first shows an overview of the three main BI integration points between Microsoft SQL Server 2005 and the 2007 Microsoft Office system:
The second part of the paper breaks down each of the above integration points by showing what software components are needed, features and benefits, how to install and configure the components, and how to use them.
A more general discussion of BI can be found here.