Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.

Hometown Tourist - Local recommendations to discover the best of the city

Event Hunt - Startups and Tech Events Curated By Locals

inviita - inviita is a free app that instantly creates tours that match your mood, in any city in the world.

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

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.