* you can export to HTML any notebook, not just public notebooks
* notebooks that include addresses can be visualized on a map and converted into a personalized map
* public notebooks already had feeds, but it's much easier to subscribe to the feeds by clicking on "export as RSS" in the Tools menu (ironically, Google uses the Atom format). This should be useful to track the changes in collaborative notebooks.
Google Notebook integrates with a lot of Google services: you can find a "Note this" option next to Google's search results, there's an option to import some text from public domain books in Google Book Search, Google Bookmarks are added to a special notebook, you can export a notebook into Google Docs to create a document or to save it as PDF, the latest version of Google Toolbar for IE integrates with Notebook, there's an iGoogle gadget and a cool integration with Blogger thanks to the hAtom microformat. Google Notebook is actually a web clipboard, a bridge between web applications and I expect to see options to identify structured content, bookmark videos, events, contact details, code snippets and more.
{ Thanks, AniMatrix. }