Earlier today I shared a video about using 81Dash as a moderated backchannel tool. In the past I've published videos about using TodaysMeet and Tozzl for the same purposes. All of those videos are included in the playlist embedded below (there are two videos about TodaysMeet).
Back in April I hosted a free webinar about using backchannels in the classroom. The recording of that webinar is embedded below.