Just read fantastic news from Erika Ehrli Cabral that the Open XML SDK 1.0 is now available. She writes:

"The Open XML Format SDK Technology Preview simplifies the task of manipulating Open XML packages. The Open XML Application Programming Interface (API) encapsulates many common tasks that developers perform on Open XML packages, so you can perform complex operations with just a few lines of code. Using this API, you can programmatically generate and manipulate Word 2007 documents, Excel 2007 spreadsheets, and PowerPoint 2007 presentations. The programming model uses managed code, so it's safe for server-side scenarios.

The Open XML Format SDK also provides how-to articles and reference documentation that can help you get started with Open XML programming."

See her post for details on where to download.