I have just encountered the natural enemy of the non-windows world: the .docx!
Much to my disgust, some of my lecturers have decided to post up their lecture notes in docx format! To anyone not aware of what this is, it is the default format which word 2007 saves its files as. And it is quite annoying to all those who don't/choose not to/too broke to get a copy of word 2007.
But my mac has come to the rescue; in a fit of rage I attempted to open such a file, and found that the mac can in fact open a docx file without word 2008! The formatting isn't fantastic, but if you are just wanting the content of the document it is sufficient.