EssentialPIM - EssentialPIM is a free Personal Information Manager that keeps up with the times and lets you manage appointments, tasks, notes, contacts, password entries and email messages across multiple devices and cloud applications.

Pintask - Pintask is the most customizable Kanban board.

Todo.txt - Track your tasks and projects in a plain text file, todo.txt. A todo.

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

Task Coach - Task Coach is a simple open source todo manager to keep track of personal tasks and todo lists.

buckets.co - Feature rich kanban board collaboration platform.