The test team has been very busy this year working on OneNote 2010 (you can get the beta here: http://www.microsoft.com/office/2010/en/default.aspx). While we have not had a tremendous amount of free time to create powertoys, I can still dig up the ones that we gave out this year.
Like I said, not a tremendous output. But OneNote itself is so great, what else do we need to add :) ?
If you want to write your own addins, a great starting point is the OneNote Developer Center at http://msdn.microsoft.com/en-us/office/aa905452.aspx. The schema reference is a must read as well - it would have saved me a few hours had a I read through it before starting on some of my addins.
Questions, comments, concerns and criticisms always welcome,