According to the Office for Mac Team Blog, a free converter for Office 2007 Word documents is available for OSX. Geoff Price writes:
"Why a stand-alone converter application? We chose this route because it supports both Office 2004 and Office v.X for Mac users, while providing some bonus functionality such as batch conversion... The user interface for the converter actually began life as an internal test tool (where you can imagine the batch processing comes in handy) - it was so slick it quickly became obvious that it was a great solution for the converter. You can drag and drop files onto the converter icon or application of course, but can also simply double-click .docx files to invoke it."The aptly named Microsoft Office Open XML File Format Converter for Mac 0.1b, otherwise known as MOOXFFCM.1b (pronounced mōō-zffc-mmm-dŏt-wŭn-be, it helps if you speak the Tlingit dialect of Na-Dene) can be found here.