Flickcall - Flickcall is a privacy-focused browser extension to watch movies & TV shows together.
Netflix Party - Netflix Party is an extension for watching Netflix remotely with friends and family for movies nights with that long-distance special someone.
Hyperbeam - A better way to watch together online
StreamParty - StreamParty is a watch communiry, that allows you to watch video streams in sync with the people you care about, on multiple services.
Metastream - Watch streaming media with friends
Togetherly - Watch Youtube with friends