EventsBase - Find the best professional events nearby or globally
Alkarta - Find happenings in your city.
Rally by Eventbrite - Find the best local events and rally your friends to join
Party with a Local - Party with a Local is a free app that connects travelers with locals that want to party.
tophitterpro - the best tennis nearby
Leisure Time - Leisure Time is an Android, iOS, and Web App that allows users to find leisure time activities in their vicinity that might interest them.