Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
Kibii - Discover exciting things to do!
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
Klook - Discover & book amazing experiences at exclusive prices
Bigtent - BigTent is a web-based organization and communication portal for groups.
EventsBase - Find the best professional events nearby or globally