Loxi - Easily add an events calendar to any website.
Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
Future - Calendar events around the clock
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.
Calendar by 44 - Blazingly fast calendaring
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets