Wikivoyage - the free worldwide travel guide that anyone can edit.
Wingder - Meet fun people nearby in pairs
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.
Heaps - Tinder with your friends. Party in a group.
Triptipedia - Triptipedia is a free collaborative encyclopedia of travel tips, where everyone can browse, save and share tips for better travel!
Arrivedo - Curated local experiences around places to stay worldwide.