Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
Apple Events for macOS - The unofficial Apple Events app for macOS
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
Facebook Local - Discover places to go and events happening near you
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.
TechEvents.co - Tech and startup events aggregator