Without any implication that it's at all okay that Apple hasn't bothered to implement a Task List application on the iPhone, here's a method I thought up to emulate task lists using the Calendar application:
- In your computer's Exchange client (you can't do it on the iPhone; you have to use Outlook or Entourage or whatever on your computer), create a new sub-directory of your current Calendar (and make sure you set it to be of the Calendar type). Call it Tasks.
- Repeat the above step with the exception that this time call the sub-directory Completed Tasks.
Pretty simple, huh? So how do you use it? Well, when you enter the Calendar application on the iPhone, you'll be able to view the calendars for your Exchange account (when you're in the Calendar app looking at the main view, you should see in the upper left-hand corner a button labeled "Calendars" that will take you to view the calendars). You'll see that you can view just one calendar or all of your calendars; as you may also know, your main view choices include List--so you can choose to view the "Tasks" calendar and view it as a List, very much as you would expect to view tasks in a Task List application. And of course you add a new task by creating a new calendar item in the Tasks calendar.
Unfortunately, there's no way to designate a calendar item as complete; that's why I use the second calendar called Completed Tasks. But there's one more unfortunate thing (referenced in my iPhone 2.0 Insights blog post) that comes into play here: you can't move calendar items from one calendar to another on the iPhone. Totally inexplicable pain in the butt, but it isn't the end of the world to just move the items over on your computer (if you don't care about completed tasks, you can always just delete them on either the iPhone or your computer and not worry about the Completed Tasks calendar).
Using 2 directories and calling them "Tasks" and "Completed Tasks" is just my choice: obviously, you can change the names of the calendar sub-directories as you see fit and you can create more than just 2 if you'd like.
Note: this definitely works with iPhone synched up over the air with Exchange; it may or may not work in other configurations (all I can say is that prior to synching over the air with Exchange, I was not aware of any way to synch with multiple calendars nor to view multiple calendars on the iPhone).
Note: I am aware that there are 3rd party Task List applications available for iPhone, however, given that none of those are able to synch with Exchange, they do not suit my purposes. I also don't know if any of those can alert me like calendars items can.