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.
Remember The Milk - Remember The Milk is a task and time management application for mobile devices.
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.
Jira - The #1 software development tool used by agile teams. Jira Software is built for every member of your software team to plan, track, and release great software.
Toodledo - Toodledo provides a set of tools to increase the productivity.