Doodle - Make meetings happen. With Doodle, scheduling becomes quick and easy.
Right Inbox - Schedule Emails in Gmail To Be Sent Later
PHP Event Calendar - PHP event calendar script with multiple views and many customizing options.
EmailPlayground - EmailPlayground provides solution to schedule and send emails with ease.
The Receptionist - The Receptionost is a visitor managemnt solution that has visitor logging system to track visitor traffic.
SendLater - Email scheduler for Mac Mail.