What are some alternatives?
Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
SkillMint - Find, meet and rate people with common skills and interests. Community-driven rating system.
Picatic - Picatic encourages event organizers to create a custom website, sell tickets and then determined their cost of use. Selling out events is easy with Picatic.
Mobilizon - A free and federated tool to get our events off Facebook
Get Together - Get Together is an open source event manager for local communities.
Openki - Platform where you can search, propose, take part, help organize or publish workshops, lectures...