MJML - The open source framework for responsive emails
Habit List - Create good habits and break bad ones with the app that keeps you focused.
Stripo - Stripo is an all-in-one email design platform. We enable our clients to build emails of any complexity, including interactive AMP emails, really fast and easy.
Momentum - Agile goal and performance management
Templates by Email Monster - Hundreds of free, responsive email templates. Pick and edit.
Streaks - The to-do list that helps you form good habits.