One of my favorite sites (and lifesavers) has been Remember the Milk [1]. I've raved about the text messaging reminders, and the fact that you can create custom lists and share them with others, which has made my life so much easier. Especially since I have trouble remembering when to take the trash out. Well . . . sometimes.
So my relief hit an all-time high when Remember the Milk came to the iTunes App Store [2]. And the best part? If you're a proud Pro account holder, it's still free! Free to get organized, free to manage my time, and free to share my tasks with my BF — cause you know, that grocery shopping won't get done on its own.