Wikivoyage - the free worldwide travel guide that anyone can edit.
Detour - Immersive audio walks, now in 17 cities
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.
Airbnb Trips - Travel and experience trips with locals
Triptipedia - Triptipedia is a free collaborative encyclopedia of travel tips, where everyone can browse, save and share tips for better travel!
Party with a Local - Party with a Local is a free app that connects travelers with locals that want to party.