Lol depends on your definition of "helpful". I got a few channels I like.
Croquis Cafe is a super awesome resource channel. It's a production company specializing in instructional videos for artists. Pretty much all their videos are free 20, on video, life drawing sessions. (NSFW FOR NUDITY)
Will Terrell's channel is also great, pretty much just an artists posting art vids. I particular like his 'People Sketching' series where he just talks about his experiences, and makes suggestions to struggling artists while he's drawing people.
This episode in particular is what got me into watching his stuff:
The Webcomic Relief is a guy who reviews webcomics. He is one of the more passionate reviewers, and he does have some interesting opinions on story, characters, and comic creation.
Scott Burdick. If you're a super pretentious art lover like myself you may find this guys videos interesting. He mainly does interviews and talks about art. The video that really drew me to check his stuff out was the 'Banishment of Beauty' video.
I dunno, I found it to be good background noise, and lead me to some artists I didn't know about.
Here is a video showing four Disney artists doing a life drawing session with a tree. The clip is a great example of how realism isn't required when using life as a resource.
This last one but Ira Glass is more of a motivational video rather than an instructional one, but when I first started out with comic it helped me out a little.