There is an Export to RTF option in the export dialog if you first click inside a text frame, and RTF can be read by Word. This will only export the text of the *story*, not "all" text.
If you have more than a single (possibly threaded) story and you want all text output into a single file, you'll need something like Rorohiko's Text Exporter (http://www.rorohiko.com/wordpress/indesign-downloads/text-exporter/).
To write all stories into separate files, all you need is the sample Textexporter script (or sth. like that) that comes installed with your InDesign.