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.

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.

Redmine - Flexible project management web application

Listium - Share your lists

Basecamp - A simple and elegant project management system.

Procezo - Free task management tool, for life.