Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
Loxi - Easily add an events calendar to any website.
Calendify - Calendify is an event community where you can share, publish, and subscribe to event calendars. It helps you to stay informed about what you are interested in and what is yet to come.
Future - Calendar events around the clock
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
Whenever - Casual calendar app for iOS