What are some alternatives?
Todoist - Todoist is a to-do list that helps you get organized, at work and in life.
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.
WorkFlowy - WorkFlowy is an organizational tool that makes life easier. It's a surprisingly powerful way to take notes, make lists, collaborate, brainstorm, plan and generally organize your brain.
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.
Zenkit - Zenkit is the home you always wanted for your ideas, your projects, your business.
Basecamp - A simple and elegant project management system.