Doit.im - Doit.
Task Coach - Task Coach is a simple open source todo manager to keep track of personal tasks and todo lists.
The Hit List - Your life is complicated, but managing it doesnt need to be.
TickTick - TickTickis a cross-platform to-do list app & task manager helps you to get all things done and make life well organized.
Conqu - Conqu is a simple yet powerful task management tool designed to help you conquer your inbox and get things done.
Todo.txt - Track your tasks and projects in a plain text file, todo.txt. A todo.