Google Duo - Google's answer to Facetime, high-quality video calling on iOS and Android.

FullCalendar - FullCalendar is an open-source JavaScript event calendar.

GoRemote - A free & simple yet powerful European based solution to go remote. Video & audio conferences, screen sharing & chat with end to end encryption. Keep your team close and productive

Dudle - Dudle is an online scheduling application, which is free and open source.

Around - Find people to hang out with.

Mobile-Calendar - Reservation management system. If you rent accommodation, the mobile-calendar app was made for you!