Dudle - Dudle is an online scheduling application, which is free and open source.
BookSteam - BookSteam Online booking and appointment scheduling software for businesses worldwide. Easy to use, cloud based web scheduler that includes class and group bookings. Calendar management and schedule organization, trusted by thousands.
Pulse 24/7 - Booking & scheduling mobile app for service providers
Acuity Scheduling - Automate your client bookings, cancellations, reminders & payments using the worlds friendliest online scheduling software.
Time Slot Booking Calendar PHP - Time Slots Booking Calendar PHP for online appointment booking and class scheduling.
MINDBODY - Find and book fitness and beauty classes near you.