On the DiRT Directory: http://dirtdirectory.org/node/644

Trello is a web-based project management and collaboration tool that allows users to organize projects in a dashboard view, containing one or more project-oriented boards. The dashboard provides a real-time overview of what is being worked on, who is working on what, and overall progress toward project milestones. Useful for organized task management, delegation, communication, and collaboration across teams.