HTMLEmail.io - Responsive HTML email templates for startups & developers
Startup Stash - A curated directory of 400 resources & tools for startups
Templates by Email Monster - Hundreds of free, responsive email templates. Pick and edit.
Content Marketing Stack - A curated directory of content marketing resources
MJML - The open source framework for responsive emails
StartupResources.io - Tightly curated lists of the best startup tools