As was announced at the annual Press Day, Google Notebook is set to make it's debut this week. As others have spotted in the Google Blogoscoped Forums, www.google.com/gn now redirects to /notebook rather than /notebook redirecting to /gn -- an attempt to make the URL a bit more user friendly I would assume.
On top of that, a new entry into the robots.txt file tells spiders not to crawl "/notebook/search?". It's only a matter of days until Google Notebook is launched. Users in the Blogoscoped forums are putting their guesses in as to the release date -- right now the popular vote is Wednesday.