[Andrew May] For the Service Pack 1 (SP1) Preview, OneNote 2003 has added extensibility functionality that enables applications to interoperate with it in an important, fundamental way - they can add content to OneNote notebooks. You can now push content to OneNote that includes html, images, and even ink (such as from a Tablet PC). You can even create the folder, section, or page onto which you want to place your content.

Read all about the ISimpleImport functionality of OneNote SP1.