i3 - A dynamic tiling window manager designed for X11, inspired by wmii, and written in C.
Streaks - The to-do list that helps you form good habits.
dwm - dwm is a dynamic window manager for X. It manages windows in tiled, monocle and floating layouts. All of the layouts can be applied dynamically, optimising the environment for the application in use and the task performed.
Taskful - Deadlines, meet your match.
Openbox - Openbox is a highly configurable, next generation window manager with extensive standards support.
Todoist - Todoist is a to-do list that helps you get organized, at work and in life.