Open Office reads Microsoft Word 2007 documents out of the box. Mac OSX comes with an unzip utility out of the box so it would make sense you receive on your MAC a zipped Word 2007 document and you will read it without any problems.
The reality is that at least in my latest Mac Book Pro (2009) when I double click the zip file it gets extracted in a folder full of XML files which Open Office will not recognize.
Of course from command prompt your old friend "unzip" will do nothing more than extracting your file but Finder will not. Somehow it is so smart that it will decompress the doc file as well (Yes the .doc you get from Microsoft 2007 is no more than a zipped bundle of XML files and more)
Now, if you are on a MAC you love GUI ;-) and so allow me to recommend http://www.edenwaith.com/products/guitar/ for uncompressing. It is a wrapper of command line utilities that do not go any smarter than what you need.