Commune
I really like the idea of watching streams or events as a group experience, but stream chats(especially pros laddering or big events) tends to be dominated by people I don't know, so I was looking for a way to have private chatrooms integrated with streams. It's sort of similar to synchtube in that it allows multiple people to watch along, but I've added some interesting features. It currently supports Youtube and Vimeo videos, as well as Twitch.tv and Justin.tv streams.
Firstly it's easy to share your private chatroom for a stream, since it's an IRC channel people can connect either through the web-client (with the big share button) or through IRC
Secondly I've created a bookmarklet to make creating a room almost instantaneous. Just drag the link into your bookmark bar and click it on a page with a Youtube/Vimeo video or Twitch/Justin.tv stream and you'll get a private chatroom watching the video. This works on their own sites or with embedded players, like TL streams.
This was a weekend project, a lot of fun to write. By the way if anyone is interested in art I'm drawing over at Tumblr now, mainly Game of Thrones characters.