I have been working with the MSDN folks to get the OneNote XML schema reference posted online. You can find them here: 2007 Office System: XML Schema Reference (Beta 2) (same link, but just better for search engines/crawlers: OneNote 2007 Beta2 XML Schema Reference).
Some notes about the OneNote reference:
Please let me know what questions you have about this. Take care!
I wanted to point out an update to the OneNote 2007 XML Schema. You can download it here: OneNote 2007