There is no end to productivity apps that you can pay for, if that is what you want to do. What is rare is finding a completely free and high-quality app. Super Productivty may be an exception.

This free and open-source application, available for Windows, Linux, Mac and Android devices, combines a to-do list, time tracking and time blocking. It allows you to quickly create a list of things you need to do, estimate how long it will take to do each one, and plan your time accordingly. The application is also built to track the time spent on those tasks, so you can find out how much time you actually spend on things.

When opened, Super Productivity shows you your Inbox, where you can dump tasks as they occur to you. You can also set up projects and put your tasks there, if you like. After you create your tasks, you can add estimates for how long they will take and even assign due dates. Then you can go to the Today, Schedule, or Planner sections and get organized.

The basic idea is that you can drag tasks into the order you want to do them. The Today section shows you a simple list. The Schedule section shows everything on a calendar (which can also show appointments from any iCal calendar, including Google and Outlook). And the Planner breaks the list into days. You can drag items from day to day, if you like.