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.
Wikivoyage - the free worldwide travel guide that anyone can edit.
Hometown Tourist - Local recommendations to discover the best of the city
inviita - inviita is a free app that instantly creates tours that match your mood, in any city in the world.
WikiOverland - WikiOverland is the community encyclopedia of Overland Travel.
VoiceMap - VoiceMap offers location-aware audio tours created by local storytellers. Tours can be downloaded to a mobile app and audio tracks automatically start playing triggered by GPS. VoiceMap also lets you sign up as storyteller and create your own tour.