It's great to see the adoption of Open XML accelerating. The Compatibility Pack for Open XML has been downloaded more than 70 million times*. Countless large organizations have taken that single download and deployed that across their organizations. These numbers continue to improve in favor of Open XML.
There are a number of tools available for manipulating, processing, scanning or otherwise handling Open XML documents. As I read the forums on OpenXMLDeveloper.org, I think I can be of service by providing a list of the tools that I know about today. There may be others, but this will help folks get started who might be looking for an entry point:
Some of the available tools
Some of the Articles & Training Content