TargetProcess - Agile Project Management Web Application
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.
Taiga - Project management platform for agile developers & designers
TaskBoard - A Kanban-inspired app for keeping track of things that need to get done.
Hygger - Hygger - is an Agile project management tool with built-in prioritization.
Pintask - Pintask is the most customizable Kanban board.