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.
Elegantt for Trello - The most elegant way to manage your Trello projects
Asana Boards - A simple, visual way to track your team’s work
Hello Epics for Trello - Simplify your Trello board with parent/child relationships
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.
TunnelVision - See your next Trello tasks every time you open a browser tab