Really Good Emails - A large collection of good product email design.
Mailmeteor - Send hundreds of personalized emails with Gmail.
Email Love - Email design inspiration, templates and discovery
GMass - GMass allows you to easily schedule emails, send out mass emails and mail merge campaigns and more with Gmail! Click here to learn about more features!
Stamplia - High converting and beautifully designed email templates
Email on Acid - We make the send button safer. For every campaign, every message, and every inbox, Email on Acid has the time-saving tools you need to put your best email forward.