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.
Corrello - Dashboards for agile teams using Trello
GoodGantt - The best Gantt chart for Trello®
Toby for Teams - Better bookmarks, now with collaboration baked in 🔖
Paws for Trello - The best way to use Trello on your desktop
Fibery - Work management platform that adapts to companies and grows with them.