Dragon Responsive Email Designer - Dragon Email Designer provides an intuitive drag and drop newsletter design tool.
Revue - The easiest way to create and send a curated newsletter
Marble Responsive Email Designer - Marble helps you design beautiful and mobile-friendly emails and newsletters.
Great Email Copy - A dose of emails from around the web.
Kingmailer - Kingmailer helps you send, receive and route/forward emails.
Really Good Emails - A large collection of good product email design.