ToDo (by Appigo, $4.99) has become one of my most used apps for a couple of reasons. First and foremost, , I have a tendency to forget things. Second, my todo's are synced to my iPad, iPod Touch and desktop. ToDo uses a web based task organizer called ToodleDo to complete this magic.
Here's how it goes....I open upToDo on my iPad, enter a new task with due dates, if appropriate. Then I tap the sync tab and it floats up to ToodleDo's site. The next time I open ToDo on my iPod Touch it syncs with ToodleDo.com and voila! everything is the same. So it doesn't matter where i am, or which device I am using, I have my lists with me.
I can set alarms to help my memory even further and categorize to do's into groups so I can pay attention to work lists at work, and home lists at home. There are tags that pop up to let me know how many tasks still have to be completed and how many are overdue, if dated.
Full disclosure here, I do still forget things sometimes, but it's because I didn't assign an alarm when I should have. ToDo does it's best to help me, but I still have to tell it what to do.