The Microsoft Office 2007 system supports a whole new set of document formats. These are collectively known as OpenXML. The OpenXML format is an XML-based format that has been approved as an ECMA standard and has been submitted to the ISO standard board too. Because it is an XML-based format, it is very easy for developers to create, read, and manipulate the contents of a document programmatically. There are numerous articles and more information about how .NET developers can do that here.
But being 'open' means that any developer can work with the OpenXML format, even if they're on a different platform. Brian Jones from the Office team just posted about a new open source project that has started on Sourceforge called OpenXML4J. The OpenXML4J project is an open source library being built that enables Java developers to easily consume and produce files in the new Microsoft OpenXML formats.
This should be cool for all those Java guys that want to interact with Office documents in the enterprise!