Microsoft Office file formats:

• DOC: Microsoft Word (application/msword)
• XLS: Microsoft Excel
• PPT/PPS: Microsoft Powerpoint

New official specifications published by Microsoft on 15 Feb 2008, with supporting technologies (OLE2 Compound file format and WMF)

Documents:

• Informations from LAOLA
• AAF Association specification (v1.0.1) (PDF)
• Excel file format (on openoffice.org)
• Compound file format (on openoffice.org)
• Microsoft Word 97 Binary File Format (2001)

Libraries/tools to read/write Microsoft office documents:

• AntiWord (C)
• LAOLA (Perl)
• Jakarta POI from Apache project (Java)
• libgsf used by gnumeric and and koffice (C)
• catdoc
• word2x
• wvWare (can also read WMF vectorial pictures)
• libole2 (old, replaced by libgsf)

Software able to read Microsoft Office documents:

• AbiWord
• OpenOffice
  • Get source code
  • Tool biffdumper can be used to see XLS dump
• KWord (use libgsf)
• xls2xml (use POI)

People who know things about these file formats:

• Caolán McNamara aka caolan
• Jody Goldberg and Manuel Mausz, authors of libgsf