I learned something today about linking Outlook tasks to OneNote. I can't vouch if this works for 2003, but it sure works great for 2007.
So anyway, there's a button in the toolbar that looks just like the little flags in Outlook. You can also hotkey these by pressing CTRL+Shift+1 through 5. This automatically creates an Outlook task. If you open up the Task in Outlook, you see a direct link back to the OneNote post.
Here's how I am using it. I am sitting in a meeting taking notes on my tablet. A work item comes up for me, so I just hotkey it to a task, and continue taking notes. Later as I am looking at my Task List (managed in part by PlanPlus from Franklin Covey), I can see just enough reminder that I have something I need to work on. I open the task and am directed to the OneNote with all the supporting information. From either application, I can update the task completion or change the timeframe.
How cool is that?