Anirudh has released a beta version of his TreeView PowerToy, which launches a navigation window for OneNote. Far more condensed and quicker to expand/condense than the built-in navigation options.
The list of features keeps evolving and this is just the first beta release, so please provide him comments and feedback on his blog.

A word of caution, the Beta Version of the Tree Viewer has caused a lot of folks running Vista some problems, especially in the event of uninstalling. Recommend waiting until a more Vista stable version is made available.
A word of caution, the Beta Version of the Tree Viewer has caused a lot of folks running Vista some problems, especially in the event of uninstalling. Recommend waiting until a more Vista stable version is made available.
TreeView, for me, is the most useful onenote extension of them all — yet I am also having trouble with it — it doesn't always show up and when I tried to uninstall and reinstall, somehow, every single filetype on my computer was unregistered.
No system restore, no registry backups — I would have lost everything, if not for rollback rx which saved my bacon mid-reboot.
I didn't stop using it though — when it works, it makes onenote much easier to use.
Anirudh, thank you, should you happen to read this — and in the next release, could you please make the icon and switch a good deal flashier? even when it's visible and clickable, I miss it sometimes.
TreeView, for me, is the most useful onenote extension of them all — yet I am also having trouble with it — it doesn’t always show up and when I tried to uninstall and reinstall, somehow, every single filetype on my computer was unregistered.
No system restore, no registry backups — I would have lost everything, if not for rollback rx which saved my bacon mid-reboot.
I didn’t stop using it though — when it works, it makes onenote much easier to use.
Anirudh, thank you, should you happen to read this — and in the next release, could you please make the icon and switch a good deal flashier? even when it’s visible and clickable, I miss it sometimes.
Can I use this info on my blog using the direct link to your blog? Thanks in advance