That was the day I discovered that Microsoft has released OneNote for the iPhone [iTunes link]. Now I can continue to reference and edit my OneNote notebooks whether I'm on my desktop, laptop, or iPhone.
To make this work, you need to do what I do, which is publish your OneNote to SkyDrive. After you do that, though, changes are automatically synchronized, so you can take notes on the go and see those changes to your OneNote when you get back to the office.
OneNote for the iPhone does pretty much everything the desktop version does; you can add text and images (from the iPhone camera), add Quick Notes, and organize your notes into different books and tabs. Your notes look pretty much the same on the iPhone as they do on our desktop, with one significant limitation: the iPhone apparently can't display tables, for some reason. In its place is a note that there's a [table].
There's a lot of feedback that users have had trouble logging into OneNote. Personally, I had to try twice; the first time I got a cryptic error message. After that, though, I haven't had a lick of trouble. OneNote is listed as free "for a limited time," so you should grab it right away if you are as OneNote addicted as I am. Since the next best alternative is a program like MobileNotr [iTunes link]-- advertised as free but useless without an ongoing (and costly) subscription fee -- OneNote is a veritable steal.