There is an article up on InfoQ showing how you can use Java to work with the Open XML formats.

Go ahead and take a look: http://www.infoq.com/articles/cracking-office-2007-with-java

While the title of the article says Office 2007, you all know that Open XML is also supported in older versions of Office, as well as a number of other non-Microsoft applications. So this article can help beyond just Office 2007. J

-Brian