Just saw this over on Brian Jones' Blog, and I'm surprised this hasn't made more of a splash on the interwebs... Microsoft has just released the specification documentation for our binary Word, Excel, and PowerPoint file formats. This means that if you write another office program like OpenOffice, Lotus Symphony, StarOffice, etc., you can ensure that your app can read and write the Microsoft Office Binary file formats exactly as they were intended.
The binary documentation itself is available up here: http://www.microsoft.com/interop/docs/OfficeBinaryFormats.mspx
- Word 97-2007 Binary File Format (.doc) Specification PDF | XPS
- PowerPoint 97-2007 Binary File Format (.ppt) Specification PDF | XPS
- Excel 97-2007 Binary File Format (.xls) Specification PDF | XPS
- Office Drawing 97-2007 Binary Format Specification PDF | XPS
It's all covered under the Open Specification Promise.