Taskulu!

Todoist is a task manager thats useful, fast and easy to use.

Taiga is a full featured project management platform for startups and agile developers & designers who want a simple, beautiful tool that makes work truly enjoyable.

Asana is a web and mobile collaborative work management app that goes beyond typical collaboration software by enabling teams to track everything they're working on. With tasks, projects, conversations, and dashboards, Asana lets your team know who's doing what by when to help you get results. Use Asana for team communication, setting meeting agendas, running brainstorms, sharing files, or creating shared calendars--anything you can think of. You can also add partner integrations to customize Asana for your team with functionality like Gantt charts, time-tracking, and Google calendar sync. Asana is available on web, iOS, and Android and is free for teams of up to 15 people. »

Wekan, formerly LibreBoard, is an open-source and collaborative Trello -like kanban board application.

Kanboard is a simple visual task board software.

Basecamp is a web-based project collaboration tool that allows groups of people to share files, meet deadlines, assign tasks, and centralize feedback.

Producteev is an online task management tool that serves as your full Productivity platform (Task and Project Management, Files Sharing, Internal Communication and Productivity Apps Aggregation).

Quire is a new-generation collaborative task management tool for organizing tasks in a tree-like structure wrapped in simple and user-friendly UI.

Open source Trello-like kanban board. Based on Restya platform.

A Kanban-inspired app for keeping track of things that need to get done.

Opensource task & productivity management tool for startups, engineered based on the concepts of OKR.

Tracker is a story-based project planning tool from Pivotal Labs that allows teams to collaborate and react to real-world changes instantly. Its based on agile software methods, but can be used on a wide range of projects.