As a student, Dropbox has changed the way I operate on a daily basis. I save all my papers, readings, and syllabi on here, then access them from either my iOS devices, laptop, or desktop machines.
Being able to access all your files from anywhere on virtually any device is great, and the file sharing features make it even more useful -- no more hassles trying to send large files by email. I don't think I've burned a CD or copied a file to a USB thumb drive since I signed up. As a bonus, it helps make sure important work isn't lost if your hard drive crashes or your laptop goes missing.