Donte The Calendar - Send calendar invites using phone numbers
Vimcal - Vimcal is the world’s fastest calendar, beautifully designed for people who work remotely and live in their calendars.
Planyway - Visual project management for Jira and Trello: manage resources, build project roadmaps, use time tracking.
Clean Google Calendar - Makes Google Calendar look nicer & launches as a desktop app
Calendar Screener - Rules to manage your calendar invites.
Plan - Plan is a better way to organize.