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.

Planning Poker - Open source implementation of planning poker game (collaborative online estimation/voting tool).

Toby for Teams - Better bookmarks, now with collaboration baked in 🔖

Firepoker - Agile Planning Poker powered by Firebase and AngularJS

Wiplo - The easiest way to organize and run your business workflows.

Planning poker online - Poker pointing made simple for distributed teams