Muzli - UI/UX and Design Inspiration Chrome Extension
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.
UI Garage - Specific mobile and web design patterns for your inspiration
MJML - The open source framework for responsive emails
Design Hunt - Curated design inspiration for everyone
BeeFree.io - Bee is MailUp's drag-&-drop editor for responsive design emails.