download sun odf pluginFor obvious reasons, Microsoft is not very keen on adding native Open Document Format support in Microsoft Office so rival Sun released a free ODF Plug-in that makes your Office programs ODF friendly. 

Using the ODF Plug-in from Sun, Microsoft Office users can create, read or save documents, spreadsheets and presentations in Open Document Format (ODF) using the stand Microsoft Office programs.

The plug-in therefore offers two-way conversion of Microsoft Office documents to and from Open Document. Unfortunately, it doesn't support Office 2007 yet though the previous versions of Office are well-supported.

Download Sun ODF Plugin | Sun StartOffice [Thanks Malte]

Earlier, a similar plug-in was tested by the ODF Foundation. Microsoft is pushing it's own Open XML document format but a Garner report find it unlikely that ISO will ever adopt Microsoft's Open XML document format.

Here's how to use the ODF format in various Office programs:

In Word, choose  File - Save As and select the file format "ODF Text Document (*.odt)"

In Excel, choose File - Export ODF Spreadsheet.

In PowerPoint, choose File - Export ODF Presentation

Related: Microsoft XPS vs Adobe PDF