Really Good Emails - A large collection of good product email design.
Mailo - Mailo is an email client where you can send and receive emails to and from anyone with an email address.
Email Inspire - Discover the best of email design and marketing — Browse email newsletters from top brands.
HEY - Email at its best, new from Basecamp.
Good Email Copy - Email copy from great companies.
Horde - Horde Groupware is a free, enterprise ready, browser based collaboration suite.