Campaign Genius - Send dynamic email content through any platform, instantly.

HEY - Email at its best, new from Basecamp.

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!

InstAddr - Disposable email address application.

MailChimp Snap - Send simple, photo-based email campaigns from your phone.

Horde - Horde Groupware is a free, enterprise ready, browser based collaboration suite.