When I came to know about Ta-da List (I don’t remember how), I got very much impressed with the simplicity of the app. I able to do what I needed. So, I started using it. It became one of my favorite to-do list application. And I am using it not just as a to-do list app.
Now they retired it. But I can still access the lists I have already created and even I can create new list. It just stopped getting new sign ups. According to them, there are dozens and dozens of great free to-do list apps on the web and dozens more on the iPhone, Android, and Windows Phone. So, what are you using as your to-do list app?