If you use Microsoft Office 2004 for Mac on your Mac and need to work with people using Word 2007 for Windows in its new native DOCX foramt, take a look at...

Microsoft Office Open XML File Format Converter for Mac 0.1.1 (Beta)

With the Office Open XML Converter, you can convert Office Open XML files to a format that is compatible with Microsoft Office 2004 for Mac and Microsoft Office v. X for Mac. You can choose to convert and open one file, or convert a large number of files.