Cron - Cron Calendar.

Google Docs - Create a new document and edit with others at the same time -- from your computer, phone or tablet. Get stuff done with or without an internet connection. Use Docs to edit Word files. Free from Google.

zcal - zcal is the fastest way to schedule every meeting for Free and make it personal.

Airborn - Create and edit documents online without sacrificing your privacy

Cal.com - Cal.com (formerly Calendso) is the open source Calendly alternative.

Bit.ai - Bit is a smart real-time document collaboration platform for teams to create interactive documents, manage digital content and track document insights.