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.
Planyway - Visual project management for Jira and Trello: manage resources, build project roadmaps, use time tracking.
Corrello - Dashboards for agile teams using Trello
Sunsama - Calendar and scheduling for teams
Toby for Teams - Better bookmarks, now with collaboration baked in 🔖
Zenkit Desktop Apps - Organize your projects and team. Now on Mac, Windows, Linux.