Chemistry Diagrams in OneNote

I've become a bit of a OneNote addict, and being able to take notes at typing speed is wonderful. However, having a normal laptop has become a small hindrance in a few of my classes. One of those classes is Biology. Structural diagrams of molecules aren't easy to snap together in OneNote 2007, despite the wonderful drawing tools. So, aside from making pretty ASCII art sketches with |'s and -'s, I was wondering if there were any add-ins for OneNote or a separate program I could download that would make the job a bit easier.

On the fortunate side, most of the pictures my professor uses are usually found on the first page of a Google image search. So I've only had to make a few diagrams after class and plug them into my lecture notes.