Cron - Cron Calendar.
KosmoTime - The to do list with super powers
Cal.com - Cal.com (formerly Calendso) is the open source Calendly alternative.
EveryPlan - Routines to promote wellbeing
zcal - zcal is the fastest way to schedule every meeting for Free and make it personal.
Centered - Centered helps you get into a Flow State faster and stay there longer so you can do your best work.