What best methods to improve your productivity do you know?

Is there any software designed for improving or maintaining high productivity levels?

I wonder if you`ve heard about these methods designed espacially to increase overall productivity:

- GTD (Getting Things Done)
- Pomodoro
- 7 Habits of Highly Effective People

What do you think of them? Would you consider trying if there would be software available designed to help you start using these methods?