Brian Jones has posted a great overview of PresentationML on his blog this week. Click here for all the details.
In learning about the Open XML formats, you need to learn about the packaging itself, the three main MLs (WordProcessingML, SpreadsheetML, and PresentationML), and the APIs or tools for manipulating all of the above (which may vary depending on your development environment). Brian has covered many of the other details in the past on his blog, but this week's post is the first time that anybody has delved into the architecture of PresentationML and presented it in a simple high-level overview for developers.
If you missed Brian's presentations at Office Devcon, this is a great chance to see that bizarre graphic he's been using to show the logical structure of an Office Open XML presentation. Looks sort of like the cover of an early-70s Yes album or something. (Sorry, Brian, couldn't resist.) Highly recommended.