iPhone: Days Away is for those of you who get a little overwhelmed by complex task management systems and want a simple, elegant to-do list that simply tells you what needs to be done and when. It's not feature-rich, but that's the point: it just gets the job done, which is exactly what it's supposed to help you do.
It doesn't integrate with any other task applications, so you have to manually add your tasks. You do so by clicking the + sign, typing in the name of the task, and picking the day it's due. When you've completed the task, just swipe to delete it. That's it. The idea is to keep you focused on the things you have to get done but not planning them so specifically that you can't possible keep up (we already know how poorly that works).
This isn't a perfect solution for everyone, however. You can essentially create a similar experience with Wunderlist, which is still simple but also syncs with and works on practically any platform. And then there is, of course, Remember the Milk for those of you who need some serious features. But if you're of the mindset that to-dos should be remarkably straightforward and unencumbered, Days Away could be the task management app you're looking for.