Trello

Trello, a collaboration tool, can organize your projects into boards. At a glance, Trello reveals what's being worked on, who's working on what, and where something is in a process. All your projects, all your tasks, all of your team--organized, tracked down, and easily visible. One can easily understand the list and the card metaphor, and can start deploying Trello within minutes.

https://trello.com/