Hours - Boosting productivity through live, virtual co-working.
Cron - Cron Calendar.
Timist - Track your time, session by session
zcal - zcal is the fastest way to schedule every meeting for Free and make it personal.
Janni - Visualise how you spend your time and change your habits
Cal.com - Cal.com (formerly Calendso) is the open source Calendly alternative.