Peek Pro - Peek Pro is a fastest growing appointment scheduling software specially designed for tours and activity operators to help increase their booking reaching out to large numbers of potential customers, mostly tourists.
Baïkal - Cal and CardDAV server
FareHarbor - Reservation software for activity and tourism businesses. Low credit card processing rates, mobile friendly. Built for you.
Radicale - The Radicale Project is a complete CalDAV (calendar) and CardDAV (contact) server solution.
Rezdy - Tour operators in 73 countries use Rezdy's booking software to sell thousands of products in real-time on their website and through distribution channels.
DAViCal - DAViCal is a server for calendar sharing.