Getting Things GNOME, GTG for short. It focuses on usability and ease of use. Its main objective is to provide a simple, powerful and flexible organization tool to the GNOME desktop environment.
GTG uses a very handy text edition system for task creation and edition. The task editor can automatically recognize metadata such as tags and subtasks only by the use of a very simple syntax. If you wanna know more about this, please read
Getting Started With GTG.
GTG is by default available in Ubuntu official repository, so just search and install it from Ubuntu Software Center or use this command:
sudo apt-get install gtg
After installation, launch GTG from
Applications -> Office menu.