DisplayFusion - DisplayFusion will make your multi-monitor life much easier.
MJML - The open source framework for responsive emails
Mizage Divvy - Divvy is an entirely new way of managing your workspace.
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.
WindowGrid - Quickly and easily layout windows on a dynamic grid using just the mouse.
Templates by Email Monster - Hundreds of free, responsive email templates. Pick and edit.