What is OpenDocument?: "The OpenDocument Format (ODF) is an emerging file format standard for electronic office documents. Representing a triumph of common sense over the methods conceived before the rise of the Internet, ODF's goals are both exciting and controversial. Early adopters of the format include state and municipal governments in some near- and far-flung places, and this makes the format's progress a thing to watch. Yet innovation theory tells us there are some hurdles we all must overcome before ODF becomes a regular topic of conversation at the ballpark. Those in the know, however, recognize that we're in about the second inning of a barn-burner. So, grab a hot dog and a beer, and settle in for a classic. - Sam Hiser, ONLamp.com "

And a sample conversion:

Test.odt
Test.docx
Test_from_Ooo.pdf
Test_from_Mso12.pdf

Not really great but it is a start.

And see the SourceForge project page for this plugin.