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.
Patook - Platonic Friend Making and Community App
eventup - Find Great Event Venues in the US
Swift Polling - Swift Polling is a text and web polling and presentation platform.