I'm having a super-busy week, so I'll let others do the talking for a change ...
I just learned from Brian Jones's blog that Sun has announced they're working on adding SpreadsheetML support to OpenOffice's Calc spreadsheet program. (If you'd rather read about this news in French, check out Julien Chable's blog.)
A new article on the OpenXmlDeveloper web site covers how to display the text contents of the slides from a PresentationML document in a web page. It's a simple example, source code included, which could be used as a starting point for a variety of Open XML development projects.
Dennis Hamilton has been blogging about document formats lately, and he has a great post this week on the dangers of finding only what you're looking for, which includes some good advice for all sides of the debates that have taken place in recent weeks.
There's a lot of talk about "open" products lately, but it's not always clear what that means in practice. Dan Lyons has an amusing take on Open Client, a closed-source application that stores documents in the proprietary non-standard NSF format.
The Open XML spec is getting a lot of attention these days, and I've received a few questions lately from people who are starting to work through the examples in it. There are many great examples of markup in the spec, but in order to test them it's handy to have simple minimal documents that you can use as a testbed.
So in the attached ZIP file I've provided three documents: the minimal DOCX, XLSX, and PPTX, respectively. You can use these to insert samples from the spec and see how they work. I created them by hand with Notepad, and they contain nothing except what's absolutely necessary to have a valid WordprocessingML, SpreadsheetML, or PresentationML document.
Here's one other tip for those learning the Open XML spec: after Part 1 - Fundamentals, skip ahead to Part 3 - Primer. Part 2 covers the Open Packaging Convention, and I think it will be easier for most folks (unless you're writing an API) to learn those details after you have a sense for what you'll be packaging, which is what you'll find covered in Part 3.