From WhatIsNew.com is this top ten list of what can be done with Microsoft's OneNote. the article called "Living in OneNote" says it all. I have used my OneNote for about everything, but mostly for meeting notes, notes while on the phone, collecting all the arrangements for conferences, and the actual notes I take at those conferences. I particularly like being able to send files via the print driver to one note for collection in one spot and for marking up. If you match versions you can collaborate with a colleague and share and simultaneously mark up a one note page or section.
If you are new to OneNote or would like more, click on help while in One Note and click on the Microsoft OneNote tour menu item.