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

Google Calendar - Spend less time managing your day & more time enjoying it

Raft Calendar - A fun and beautiful calendar for couples and close friends

Business Calendar - Powerful and easy to use calendar app for Android including weather, widgets and tasks.

emble - Plan better events with your friends

Jorte - Schedule books must be practical and has a good design.