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

XCalSync - Automatically copy events between your calendars.

Event Hunt - Startups and Tech Events Curated By Locals

Social - Social let’s you plan almost anything with your connections and keeps track of it for you.

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

Evounce - Easy and fast event planning platform