Right Inbox - Schedule Emails in Gmail To Be Sent Later

Followup.cc - FollowUp for email is a lightweight productivity suite that keeps your conversations and tasks from slipping through the cracks. Set perfectly timed reminders that arrive at the top of your inbox, right when you need them.

Recurrr - Send recurring emails

Streak - Manage customers inside Gmail

FollowUpThen - The simplest way to schedule an email reminder

Kit CRM - A CRM for your Facebook page