PlanITpoker - PlanITpoker is a cool on-line planning poker app that helps Agile project teams estimate projects easily.
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.
Firepoker - Agile Planning Poker powered by Firebase and AngularJS
KanbanFlow - KanbanFlow is a Lean project management tool allowing real-time collaboration between team members. Supports the Pomodoro technique for time tracking.
Planning Poker - Open source implementation of planning poker game (collaborative online estimation/voting tool).
Meistertask - MeisterTask is an intuitive task management and collaboration tool.