OneNote is a Microsoft easy-to-use note-taking and information-management program. It is simple application but powerful. I herad some people saying that it is one of underrated Microsoft products. Some people is crazy about it after using it. One of my loved ones is using it now and he strongly recommend it. I just have MS Office 2007 installed on my computer so I am starting to use it. Here is Microsoft OneNote Demo page and a couple of other blogs that introducing OneNote features.
OneNote-note taking power tool
OneNote + Tablet + VS: Great iteration tools