OneNote is more than just a great note-taking tool (although it definitely excels at that). It can also be an excellent personal planner, and depending on how you use it, it can be a pretty solid personal project manager. We shared some of our favorite OneNote tips in our guide to being productive with what you have at the office. Among more than a few project management-focused designs to help you organize complex projects with lots of to-dos and moving parts. Using OneNote as a project management tool can be tricky, since it's not especially good at giving you a quick, top-down view of everything that's going on at once, but there's no reason you can't build that yourself using the tools available. Plus, once you power up OneNote with plugins like OneTastic, or keep your files in SkyDrive (where you can get to them and your projects using the OneNote apps for iPhone, iPad, and Android), you'll find OneNote can be a remarkably powerful tool.
The only downside to OneNote is the price. It's part of Microsoft Office, but you don't have to buy it along with Office. A stand-alone version will set you back $70. If you do want it as part of Office, you'll have to shell out some cash to get a licensed copy, either with a copy of Office for yourself, or a subscription to Microsoft's cloud-based office suite, Office 365. How much depends on your situation. If you have access to it at work or through a student discount, take advantage of it.