The team @ Intergen (Simon 'Skip' Gardiner of Kognition fame was the project lead) have been beavering away recently on an Open Source application for parsing and reporting on IIS log files.

It's called IIS Log Analyzer and it shows how easy it is to use the Office Open XML file formats to do document generation.

While the application is hosted inside Excel (by way of Visual Studio Tools for Office) all the document generation is done with plain old XML generation and some help from the .NET packaging APIs.

OOXML really does open up a wealth of additional options for doing document generation really easily.

Check it out here:

http://www.codeplex.com/IISAnalyzer