Cronofy - Unified Calendar API for developers
Raft Calendar - A fun and beautiful calendar for couples and close friends
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.
Onin - Plan events without leaving the conversation
Calendarix - Calendarix is a powerful and easy to use web-based calendar that runs on PHP and MySQL.
Ddays - Plan events with friends without the back and forth messages