I wrote previously about a solution for printing to OneNote 2007 on 64 bit OSes that I created called XPS2OneNote.
I just released an update to that solution that:
Note: this also works on Vista 64 bit and 32 bit Windows 7 or Vista.
Go to the codeplex site for XPS2OneNote to download it and install it. Please read the instructions for how to use it. You’ll need to restart your machine or manually start XPS2OneNote after installing it.
NOTE: this is not necessary for OneNote 2010 Beta. OneNote 2010 has full 64 bit support for the Send to OneNote 2010 print driver.