Dudle - Dudle is an online scheduling application, which is free and open source.
Doodle - Make meetings happen. With Doodle, scheduling becomes quick and easy.
FullCalendar - FullCalendar is an open-source JavaScript event calendar.
Framadate - Make your polls
OpenSondage - Make your polls with OpenSondage.
Xoyondo - Xoyondo makes it easy to find a date for your event that works for everybody. You can also create polls and conduct surveys. Xoyondo is free. No registration required.