task is a console-based to-do list manager with facilities to do everything you can imagine with the lists. As a student I’ve used dozens of to-do list managers and have never come across a better application.
The fact that this is console-based can be daunting to some, but believe me, getting used to task is a piece of cake.
In Ubuntu, you can install task by running

sudo apt-get install task

To add a task, run

task add Buy soap

To view the task list, run

task ls

To mark the first task as done, run

task 1 done

All other tasks are similarly simple. You can duplicate, prioritize, manage in projects, tag, modify and annotate tasks. For a more comprehensive tutorial check the Taskwarrior site.