Webvizio - This free website feedback tool & website review software allows managers and teams to collaborate on website revisions in real time. Join for free now!
HTMLEmail.io - Responsive HTML email templates for startups & developers
Collaboration Toolkit by Mailjet - Think Google Docs for email template creation 💌
Templates by Email Monster - Hundreds of free, responsive email templates. Pick and edit.
DebugTool - A single screen that let you see what needs to be fixed quickly and easily in your webdesign.
MJML - The open source framework for responsive emails