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.

Asana - Asana project management is an effort to re-imagine how we work together, through modern productivity software. Fast and versatile, Asana helps individuals and groups get more done.

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

Wrike - Wrike is a flexible, scalable, and easy-to-use collaborative work management software that helps high-performance teams organize and accomplish their work. Try it now.

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

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