Trello - Infinitely flexible. Incredibly easy to use. Great mobile apps. It's free. Trello keeps track of everything, from the big picture to the minute details.
Canary Mail - Privacy-aware email app for Mac & iOS
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.
Flow-e - Turn your Gmail or Office365 inbox to a Visual Task Board.
Basecamp - A simple and elegant project management system.
Airmail - Airmail is a lightweight and lightning fast mail client for Mac.