Workflowy - A better way to organize your mind.
Todoist - Todoist is a to-do list that helps you get organized, at work and in life.
Checkvist - A professional list-making tool. Minimalist, keyboard-centric online outliner and task management application. Free sharing, unlimited lists, cross-linking, free import and export. Markdown support. Created for geeks 🤓 and all keyboard lovers ⌨️
Todo.txt - Track your tasks and projects in a plain text file, todo.txt. A todo.
OmniOutliner - OmniOutliner is a writing app for collecting information, outlining ideas, adding structure to any sort of writing.
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.