My colleagues on the Office Interoperability team have been hard at work on a tool that will help implementers of the Office binary formats identify and correct any issues in binary documents created or modified by their software.  The Binary File Format Validator Beta is now publicly available here, and Michael Bowman has a blog post covering the details. In Michael's words:

BFFValidator runs as a command line without a dependency on the Office product. BFFValidator is targeted towards binary file format developers and generates prescriptive failure information when a given file does not conform to the Open Specifications. The tool will generate an XML log file that will correlate the issue with a specific section of documentation, the stream offset where the failure occurred, and other pertinent debug information. To learn more, please check out the BFFValidator reference file on the dowload page and stay tuned for a "How to guide" to be published on MSDN.

If you're working with the binary formats, this is a great tool for assuring the best possible interoperability with other implementations. Check it out, and if you have questions about the tool you can get those answered at the Microsoft Open Specification support alias, dochelp@microsoft.com.