Google Calendar - Spend less time managing your day & more time enjoying it
Lightning Calendar - Organize your life — it’s about time!
Mixmax Calendar - The fastest way to schedule meetings with anyone, anywhere
Simple Calendar - A simple calendar with events (optional recurring and reminders), week numbers and a customizable...
Sunsama - Calendar and scheduling for teams
GMinder - GMinder is an open source Windows System Tray app that pops up to remind you about Google Calendar events.