LeanBoard - Collaborative board with sticky notes for your GitHub issues
Nifty - Manage projects, work, and communications in one place.
Sendtask - Sendtask is the easiest way to organize your work and collaborate online. Simple to use but powerful enough to run your business on it.
ZenHub - ZenHub is how the world's best software teams work together. Trusted by NASA, Docker, and Rackspace. Start free today!
WhoCan - WhoCan lets you manage photo and video productions in one place.
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.