Great info from Brian Jones on the Open XML standards as well interop solutions.
Ecma Standard 376 – Office Open XML formats
It's finally official. Today the Ecma General Assembly voted almost unanimously to approve the Office Open XML formats as an official Ecma standard. They also voted to submit the standard to ISO for fast track certification. The official press release from Ecma International can be found here: http://www.ecma-international.org/news/PressReleases/PR_TC45_Dec2006.htm
I'm looking forward to all the smaller companies (like the folks participating up on openxmldeveloper.org) that take advantage of this interoperable format as a building block for rich solutions that create and consume documents, spreadsheets, presentations, and other document types we haven't thought of yet. There are simple tools out there like the docx converter (http://docx-converter.com). There is the open source project up on sourceforge for converting from Open XML to ODF and back (http://odf-converter.sourceforge.net/). There is even the MindManager tool that converts mind maps into wordprocessing documents. The possibility are infinite… who knows how long it will be before we even see things like rich spreadsheetML files with branding, charting, pivot tables, etc. being output directly from hardware devices (like medical imaging equipment) rather than a basic CSV file.