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.

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.

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

Procezo - Free task management tool, for life.

Evadastudio - The web application that has all the tools that you need to accelerate your company under one roof.

Remember The Milk - Remember The Milk is a task and time management application for mobile devices.