Meetingbird for Gmail - View your calendar and schedule meetings right from Gmail
Cron - Cron Calendar.
Kin Calendar - The simple and connected calendar
Vimcal - Vimcal is the world’s fastest calendar, beautifully designed for people who work remotely and live in their calendars.
Calendly for Chrome - Schedule meetings without leaving your inbox
KosmoTime - The to do list with super powers