DownToDash - Meet fun people based on activities & discover events!

Party with a Local - Party with a Local is a free app that connects travelers with locals that want to party.

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

Palaround - Meet people you should be friends with.

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

Babble - A more personalized social network