I have mentioned this in the past that OneNote 2007 will support toolbar addins and I have been silent on them recently. This is because the toolbar buttons didn't work in Beta2 that came out back in May, however they will be working when B2TR comes out.
That being said I will have the following documentation:
- A nice step-by-step document on how to create your own addin
- A simple download project to test (though you would need to change a bunch of GUIDs to make it your own)
Looking forward to seeing what the developer community does with this. If you have questions please let me know.