Wingder - Meet fun people nearby in pairs
Wikivoyage - the free worldwide travel guide that anyone can edit.
Heaps - Tinder with your friends. Party in a group.
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.
Google NightWalk - An audio Streetview tour around Marseille
Triptipedia - Triptipedia is a free collaborative encyclopedia of travel tips, where everyone can browse, save and share tips for better travel!