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.
Amium - A collaboration app that brings conversation to your files
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.
Dropbox Paper - A collaborative document-editing service
Infinity - Infinity is a fully flexible work management platform where you can organize all your work, your way.
Dropbox Paper Mobile - Organize your team’s knowledge in a single place