Couchers.org - The new alternative to Couchsurfing. Non-profit. Community-focused. Well built.
Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
Couchsurfing - CouchSurfing is your ticket to explore the world -- from the road or from your own home.
Event Hunt - Startups and Tech Events Curated By Locals
Trustroots - Travellers community for sharing, hosting and getting people together.
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets