I have watched quite a lot of them, and George is right, there are some pretty bad practices shown in some videos. OTOH, the Wyoming Woodturner is pretty good and has some "basic techniques" videos out. I've seen some of Lyle's and they are also good.
Jimmy Clewes also has a few videos out (mostly from demos at clubs in the USA) and they are pretty good. I have even found a series of videos from Ray Key, where he explains all the basics of bowl turning.