Well, not built-in, but today's announcement of the Open XML Translator, an open-source project to deliver an ODF add-in for Word 2007, means that you'll be able to easily create ODF documents from Word 2007 if your organization has standardized on ODF. And Excel/Powerpoint versions of the converter will be available some time next year. I love this news, because it means we can stop talking about ODF support as if it's a "missing feature" and instead focus on which desktop apps deliver the best functionality, performance, and ease of use.
Brian Jones has a great overview of the announcement and its implications, and Stephen O'Grady has some interesting commentary as well. After a development like this, can flying pigs or hell-frozen-over be far behind?