Dudle - Dudle is an online scheduling application, which is free and open source.
Asana - Asana project management is an effort to re-imagine how we work together, through modern productivity software. Fast and versatile, Asana helps individuals and groups get more done.
Pulse 24/7 - Booking & scheduling mobile app for service providers
Meekan - Connecting the world's calendars
MakePlans - Online appointment booking - MakePlans
Standuply - Run daily standup meetings and track your metrics in Slack