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.

Motion Firefox - All-in-one time management tool in Firefox

Todoist - Todoist is a to-do list that helps you get organized, at work and in life.

Task Muncher - Task Muncher is a cross-platform and web-based application that is designed to organize and keep the track of everything and focus on munching the weekly tasks.

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.

Taskable - Using multiple work apps leads to tons of context switching, breaking flow and killing productivity.