Dudle - Dudle is an online scheduling application, which is free and open source.
Task Muncher - Task Muncher is a cross-platform and web-based application that is designed to organize and keep the track of everything and focus on munching the weekly tasks.
Pulse 24/7 - Booking & scheduling mobile app for service providers
Vagaro - Vagaro is a salon software for booth renters, small salons, or multi-locations.
Time Slot Booking Calendar PHP - Time Slots Booking Calendar PHP for online appointment booking and class scheduling.
TideTask - Control your procrastination and never miss a task again