Dudle - Dudle is an online scheduling application, which is free and open source.
Letsfind - Letsfind is a fast, easy-to-use, ad-free way to create online (meeting) polls.
FullCalendar - FullCalendar is an open-source JavaScript event calendar.
Framadate - Make your polls
FreeBu - Smart free/busy calendar sharing and meeting organizer.
Doodle - Make meetings happen. With Doodle, scheduling becomes quick and easy.