Mailmeteor - Send hundreds of personalized emails with Gmail.
Lob - A simple API to integrate print & mail solutions into your applications.
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!
PebblePost - PebblePost invented Programmatic Direct Mail® to transform real-time online activity into personalized, dynamically rendered direct mail.
Interseller - Interseller helps find contact information, reach out to them with email automation and syncs it all into your database.
Squarespace Email Campaigns - Email, but pretty.