I used to use a Windows Mobile phone, so my life was dictated by the Tasks feature. Sad to see that Apple can't provide something basic that's comparable.
That said, I use Appigo's ToDo. Yeah, it costs $9.99, but that's a small price to pay for sanity. Plus, it does a damn good job with its interface and ability to view offline tasks.
Another school/business app you might consider, Doju, is a voice recording app. I know a lot of people find it useful to record everything, and then filter through it when studying. I can't recommend one yet, since I haven't really used any of them out there.