It's been a fairly busy year for the OneNote test team.  One way I can give some "proof" for that statement is by looking at the number of powertoys the test team gave out over the past year.  Frankly, there have not been that many, and most of the results here are merely updating addins from OneNote 2007 to OneNote 2010.

And for good measure, I'll add a link to Omer's (excellent) Onetastic powertoy.  He's not a tester but since he's on the team I figured I would include a link here.

New for OneNote 2010:

OneCal  Has a calendar view and image cropping.  Super fantastic extension!

Updated from 2007:

Image Importer

Sort Pages

Table Of Contents

Section Color Powertoy

Table Sum

For OneNote 2007:

Tree Control

This has been replaced in functionality with the Quick Filing Dialog in OneNote 2010.

If you want to write your own addins, here are some links to get you started.

Visual Studio (the Express editions are free)

The OneNote 2010 Developer Center:  Has links to the reference materials and lots of code samples (this is new!).

And one of our external users has written a good step by step guide you may want to study.

Malte Ahren's blog - he tells how to create Ribbon based addins: 

Thanks Malte!

Questions, comments, concerns and criticisms always welcome,