BillG talked about this site during the keynote at Office DevCon. All about open XML document formats etc.. :
The Open XML Formats Developer Group is being formed as a community for developers to exchange information with each other regarding the usage of the Ecma-developed Office Open XML file formats. The community will serve as a technical resource for Open XML developers to submit and answer technical questions and to share tools and ideas around Open XML Formats-based solutions. The Open XML Formats Developer Group is open to anyone free of charge to enable broad participation and development of solutions using the Open XML Formats on any platform. The Open XML Formats Developer Group will support the wide adoption of the specifications being created by Ecma Technical Committee 45. More information is available at www.OpenXmlDeveloper.org.