GTD (short for Getting Things Done) this time-management/self-management method was put forward by David Allen (in the field of developing potentials of individuals and companies, he is widely considered to be a world-class authority) in his bestselling book with the same title Getting Things Done: The Art of Stress-Free Productivity (first published in 2001 and revised in 2015).
First of all, Active Desktop Calendar has become an oldware now. Nevertheless, it is still a very excellent and practical desktop calendar program!
Rainlendar is a very beautiful desktop calendar application, I'm deeply attracted by it at the sight of Rainlendar: beautiful but practical, simple yet powerful.
WatchMe is a simple timer applet, it can start multiple timers at the same time, and adds memos for each one.
ToDoList is a very excellent and personalized open-source, free task management application, with a lot of details considered. Its tree structure can easily show all tasks, and allows to orderly manage your daily work and calendar arrangement.
One of the benefits of using software instead of the paper sticky-notes is to make our work environment more clean, so that the screen or office table will not become messy because of sticking around with post-it notes. Yet, StickyPad is a very beautiful desktop post-its application, which has no difference with the real one.