Mobilizon - A free and federated tool to get our events off Facebook

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

DownToMeet - DownToMeet is a platform to organize, find, and attend group events.

CooMeet - CooMeet is one of the best and leading next generation of video dating web-based application specially designed for those users who want to talk online to people they have never met.

Openki - Platform where you can search, propose, take part, help organize or publish workshops, lectures...

Get Together - Get Together is an open source event manager for local communities.