Dashblock - Turn any website into an API

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

Sheety - Turn any Google sheet into an API instantly, for free. Power websites, apps, or whatever you like, all from a spreadsheet. Changes to your spreadsheet update your API in realtime. Neat

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

Postman - The Collaboration Platform for API Development

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.