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

Happer - Meet people & participate in activities, happier together

Upcoming.org - A simple way to share and discover interesting events

Rendevous app - Swipe on parties near you.

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

PlayWith - Connect around sports and games