Dudle - Dudle is an online scheduling application, which is free and open source.
FullCalendar - FullCalendar is an open-source JavaScript event calendar.
Doodle - Make meetings happen. With Doodle, scheduling becomes quick and easy.
Framadate - Make your polls
Mobile-Calendar - Reservation management system. If you rent accommodation, the mobile-calendar app was made for you!
Appointy - Appointy is an advanced web-based scheduling software tool.