There are lots of things to like about 2Do. You can use it to manage simple reminders and checklists, as well as larger projects. 2Do also lets you organize tasks by color -- an important feature for visually oriented ADHDers.
The 2Do app is easy to use. It features a clear tab system along the left-hand side that allows you to create and color-code lists to organize your tasks by context -- home, office, errands -- or by project. Each task in your 2Do list is sortable by priorities, due dates, notes, an embedded audio note, and/or photo. You can also add actions to your tasks that link to your contacts, allowing you to call, e-mail, or text directly from the app. One practical feature for ADHDers is being able to defer tasks you didn't get done to a future date -- something, I admit, I have used a lot.
A client of mine told me that 30/30 is one of his favorite ADHD apps, so I put it through its paces. I love it, too. The app allows you to set sequential countdown timers to walk you through your day's tasks. I've been using 30/30 for a few weeks now, and I find it very helpful. Taking a few minutes each morning to set up my day in 30/30 takes the guesswork out of what I need to do next. The app has also made me keenly aware of how I -- probably like you -- underestimate how long it will take to do things. 30/30's gesture-based controls make it a snap to use.
(iOS free 30-day trial; account is $24/year)
This may be my favorite time-management app. TeuxDeux is a clear and simple task manager that reminds me of my old week-at-a-glance calendar that I left behind years ago. The app gives you a view of five days at a time, where you can assign tasks a completion date. There's room at the bottom of the screen to list tasks by project. What I like best about TeuxDeux is that you can access your account through your Web browser, and it syncs to your iPhone app. If you have an Android phone or device, you can access TeuxDeux on your browser. As much as I love my iPhone, I find the daily managing of my to-do list on it a bit tedious. I prefer the big screen of my laptop. Yet the updated tasks are on my phone for those many times when I break away from my desk and my computer.