MS Word documents (DOC)

MS Word document format is a semi-trasparent proprietary format developped by Microsoft. Part of the data it encodes are accessible, while most of them are opaque.
The same formatting and word processing capabilities of MS Word documents are supported by the "Ooo" open format - an XML-based standard developped by the OpenOffice.org free software suite, which satisfies accessibility criterions established by the W3 Consorsium. OpenOffice.org format - because of its portability and compatibility - aims at becoming the reference standard for formatted text documents.
If the text is not aimed at edition by the recipient, the best solution is to use the HTML open format, readable into any web browser, and editable into any text editor. In case a precise page formatting is needed (for instance for documents that will be printed), the PS and PDF open formats are the best solution. For scientific texts, suitable open formats are TeX and DVI.
As an alternative solution (although not optimal, it is still better than the MS Word document format), for co-authoring documents is the semi-proprietary RTF format, which, in its native form, has a specification, and can be read by almost every word-processing software.