Youtube Plus - Home of the extension YouTube Plus that allows you to experience more on YouTube - ParticleCore/Particle
Metastream - Watch streaming media with friends
GIFit! - Quickly turn YouTube videos into GIFs (chrome extension)
Watch2Gether - Watch2Gether is an app that allows multiple people to watch the same content simultaneously and interact with each other while watching.
Book Video Club - Quick video summaries of the top business books for startups
StreamParty - StreamParty is a watch communiry, that allows you to watch video streams in sync with the people you care about, on multiple services.