awesome - A dynamic window manager for the X Window System developed in the C and Lua programming languages.
Taskable - Using multiple work apps leads to tons of context switching, breaking flow and killing productivity.
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.
Things - Things is an easy to use task manager.
Wmderland - Lightweight Tiling Window Manager for X Window System
Google Tasks - to-do list app that integrates with Gmail and Google Calendar