ApPHP Calendar - ApPHP Calendar is a PHP calendar script that may be easily integrated and used with various PHP projects, such as schedulers, event, etc.
Time Slot Booking Calendar PHP - Time Slots Booking Calendar PHP for online appointment booking and class scheduling.
Availability Booking Calendar PHP - PHP Availability Booking Calendar is open source php booking system for online reservations.
Pulse 24/7 - Booking & scheduling mobile app for service providers
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MarketPress - MarketPress is the best free eCommerce plugin available for WordPress.