Dudle - Dudle is an online scheduling application, which is free and open source.
Acuity Scheduling - Automate your client bookings, cancellations, reminders & payments using the worlds friendliest online scheduling software.
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.
Framadate - Make your polls
Checkfront - Checkfront is built for Tour & Activity Operators, Rental companies and Accommodation providers. Manage your inventories online, centralize reservations, process payments and get unified access to leading distribution channels.