FullCalendar - FullCalendar is an open-source JavaScript event calendar.
Calendly - Say goodbye to phone and email tag for finding the perfect meeting time with Calendly. It's 100% free, super easy to use and you'll love our customer service.
Letsfind - Letsfind is a fast, easy-to-use, ad-free way to create online (meeting) polls.
Acuity Scheduling - Automate your client bookings, cancellations, reminders & payments using the worlds friendliest online scheduling software.
FreeBu - Smart free/busy calendar sharing and meeting organizer.
Reservio - Reservio is a simple online booking and appointment scheduling application.