Last month the Microsoft Paris office featured Open XML development at their "mercredis du développement" event, and webcasts from that event are now available on MSDN/France. Cyril Durand has posted a list of links to the webcasts.
If you speak French, these webcasts offer a variety of useful information about Open XML development. And if you're just learning French, as I am, what better way to learn than to listen to French software developers talk about Open XML? :-)
Merci pour les liens, Cyril.