I'm addicted to oneNote.
Now that I have a company in the making and a partner, I'd like to share oneNote notebooks (it beats wikis etc when we are only 2 people, it works offline better, etc).
The problem with a onenote Shared notebook: can you do it without a sharepoint server? I don't think so. But maybe you can.
If there's no way around, do you know of any way to use a sharepoint server without having to pay for an (incredibly expensive) M$ server?