Guestboard - Lead powerfully-organized group events with Guestboard – a modular event platform that gives groups of 10-1000+ people a central space to coordinate, build excitement, and save money. No more crazy email threads. No more massive group texts.
Watch2Gether - Watch2Gether is an app that allows multiple people to watch the same content simultaneously and interact with each other while watching.
Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
Metastream - Watch streaming media with friends
Mobilizon - A free and federated tool to get our events off Facebook
StreamParty - StreamParty is a watch communiry, that allows you to watch video streams in sync with the people you care about, on multiple services.