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.
Glitch - Glitch is the friendly community where everyone builds the web. Simple, powerful interface for creating web apps.
Asana - Asana project management is an effort to re-imagine how we work together, through modern productivity software. Fast and versatile, Asana helps individuals and groups get more done.
Koji - Develop and deploy web apps at a ludicrous speed
Pivotal Tracker - Pivotal Tracker: The awesome, lightweight, agile project management tool for software teams. Get your 30-day Free Trial started today!
StdLib - Discover pre-built APIs, compose your own and build apps