Dynamically Personalized Emails by QGraph - Hyper-personalized emails for E-commerce
Cron - Cron Calendar.
InboxSDK - First usable API to write Gmail Apps for 1B active users
zcal - zcal is the fastest way to schedule every meeting for Free and make it personal.
Nova Inbox - Personalize emails in seconds, right from your inbox
Cal.com - Cal.com (formerly Calendso) is the open source Calendly alternative.