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.

Kanban Tool - Simple and effective online application for visual project management.

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.

GitKraken Glo Boards - Easily track tasks and issues from inside popular dev tools

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

KanbanFlow - KanbanFlow is a Lean project management tool allowing real-time collaboration between team members. Supports the Pomodoro technique for time tracking.