SendLater - Email scheduler for Mac Mail.
Really Good Emails - A large collection of good product email design.
SndLatr - SndLatr is a Gmail plugin that makes it easy to schedule emails to be sent automatically at a later time.
Email Inspire - Discover the best of email design and marketing — Browse email newsletters from top brands.
The Top Inbox - The Top Inbox for Gmail helps to schedule emails to be sent later, set reminders in the inbox and follow up with email sequences.
Good Email Copy - Email copy from great companies.