Loxi - Easily add an events calendar to any website.
Button for Google Calendar™ - See your daily schedule and join meetings in one-click.
Future - Calendar events around the clock
Add-to-Calendar Button Generator - This open source projects lets everybody create amazing buttons, where users can add events to their calendars.
Whenever - Casual calendar app for iOS
Vimcal - Vimcal is the world’s fastest calendar, beautifully designed for people who work remotely and live in their calendars.