For several month, I've been using Remember the Milk on my iPodTouch and computer desktop. It was the only "list creator" program that I could find that worked without an Internet connection. With the iPod Touch, I am not always connected to the Internet. I can read all of my messages and lists in RTM when I'm offline and strolling through the grocery.
No more losing the list on the way to the store or leaving it in the car. You can also set reminders and sync with your calendar. It was very easy to set up and start using. I was able to do it without consulting the user guides -- yahoo.
RTM works with a lot of products -- iPhone, Blackberry, Android, Google, gMail and a bunch more. There are several third party plugins to make "remembering" even easier (like adding tasks via Jott).
Now there's no excuse when I don't Remember the Milk.