Trello - Infinitely flexible. Incredibly easy to use. Great mobile apps. It's free. Trello keeps track of everything, from the big picture to the minute details.
C-Organizer - C-Organizer is a robust software tool designed for the professional manager that permits them to organize business activities altogether.
Todoist - Todoist is a to-do list that helps you get organized, at work and in life.
Info Select - Info Select is a Personal Information Manager that organizes Internet data, notes, to-do's...
Asana - Asana project management is an effort to re-imagine how we work together, through modern productivity software. Fast and versatile, Asana helps individuals and groups get more done.
AllMyNotes Organizer - AllMyNotes Organizer is a multi-functional hierarchical information manager for Windows.