I tried a whole bunch of these iPhone apps for lists a while back. Most didn't suit my needs. One was just a To Do list that didn't let me categorize things enough, and I remember not being that impressed with Remember the Milk (I was only looking at the free versions), but you can get others that will let you put things in categories, set different alarms to go off. I'm sure there's something way better now than even when I tried all this, which might've been a year ago.

I also use the calendar app on my iPhone and have, like, 7 or 8 different calendars in it - one for Doctors, one for work, one for home, one for family, etc. It alerts me for all kinds of things.