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.
Wekan, formerly LibreBoard, is an open-source and collaborative Trello -like kanban board application.
Kanboard is a free and open source Kanban project management software.
Widget Board is a productivity tool that lets you create custom boards with your favorite widgets such as tasks, notes, media, date & time, weather, calendar and so much more!.
Leantime is a project management system for small teams and startups. Designed to help you manage your projects from ideation to delivery. Leantime's Idea Manager allows you to store ideas, communicate them with team members, discuss and move them from idea to validation.
Sametable is a refreshing alternative to 1) The all-in-one collaboration tools, 2) Always-on work culture, and 3) Attention-grabbing
Freelo is a Project Management tool that helps teams and freelancers do more with less effort. It is designed to be as simple and intuitive as possible.