Janus

Janus is an open source, highly extensible, lightweight (written in C) WebRTC Gateway made by Meetecho

You can test many of the demos on their website, such as the Video Room.

Jangouts

Jangouts (short for "Janus Hangouts") is an open source, self-hosted alternative to Google Hangouts. It's backed by the Janus Gateway and its the videoroom plugin.

See also

Videoconferencing