Dudle - Dudle is an online scheduling application, which is free and open source.
Loomio - Loomio helps groups of people make decisions together, online.
FullCalendar - FullCalendar is an open-source JavaScript event calendar.
Mentimeter - a web-based polling tool for workshops, conferences & events
Framadate - Make your polls
PollUnit - Create and customize public or anonymous votings, surveys, free tables, idea collections or audio, video and photo contests.