Flow-e is a visualization layer on top of your Gmail or Outlook inbox. It provides an elegant Kanban-like workflow that's combined with the ideas behind Inbox Zero and GTD. Flow-e eliminates the need of external task management tools and transforms your inbox into a central To Do app.
Sortd - Rated the #1 App for Gmail
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.
Drag for Gmail - Transform Gmail into organized To Do lists (like Trello)
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.
KanbanMail - A Kanban board for your emails.
Slack - A messaging app for teams who see through the Earth!