Wikivoyage - the free worldwide travel guide that anyone can edit.

Eventbrite - Discover Great Events or Create Your Own & Sell Tickets

Triptipedia - Triptipedia is a free collaborative encyclopedia of travel tips, where everyone can browse, save and share tips for better travel!

Attendize Event Ticketing - Attendize is a free & open-source ticket selling and event management platform

Tripadvisor - The Tripadvisor mobile app is available for the Android and iOS platforms. It can be used to create reviews of hotels, restaurants, and to chat with other travelers on Tripadvisor forums.

pretix - pretix helps you to sell tickets for your event in an easy way. It supports multi-lingual events and provides a wide range of features