Transactional Email Templates by Postmark - Open source email templates for use in your SaaS app.
Pistachio Email Templates - Delicious newsletter templates built for automation
SaaS Email Templates - Responsive HTML email templates for SaaS startups
Email2Go.io - Perfect emails are born here
Templates by Email Monster - Hundreds of free, responsive email templates. Pick and edit.
Great Email Templates - HubSpot email templates for SaaS marketers