Hello Epics for Trello - Simplify your Trello board with parent/child relationships
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.
TunnelVision - See your next Trello tasks every time you open a browser tab
GoodGantt - The best Gantt chart for Trello®
Paws for Trello - The best way to use Trello on your desktop
StandupScreen for Trello - Turn a magnetic whiteboard into an interactive Trello board