Slack News Feed - Get the top posts from every Slack chat you're in.
Recurrr - Send recurring emails
Top Daily Hunts in Slack - A simple, fast way to browse news within Slack
Right Inbox - Schedule Emails in Gmail To Be Sent Later
Slack It - A bookmarklet to share links in Slack with one click
SendRecurring - SendRecurring allows you to setup, send, and maintain scheduled email reminders.