I've always found youtube and google video to be a very useful tool. People are looking for, well, anything and you can find it on one of these two sites. The other day, I was looking for a movie made off of the novel "The Girl, The Gold Watch and Everything" written by John D. MacDonald in 1962 (Also famous for his Travis McGee novels). And, I found it on Youtube, made into a TV movie in 1980, starring Pam Dawber (Mork and Mindy) and Robert Hayes (The Airplane movies). Frankly, the book was a lot better.
This was the first time that I'd ever heard of TeacherTube, but I like the concept. Many colleges other schools are uploading vids of basic courses and this is a great site for students.
Overall, I would rate Google videos as the best, chiefly because they post vids from other sites as well. Sometimes you can't view the video on the Google site, but you can always follow the link back to the original site.
The video that I've posted is an example of Hsing I, one of the martial arts that I practice. What's being practiced is called the Five Element Fists and the gentleman who is doing it is not linked with our style. So, the way that he's doing it is somewhat differant from the way that we practice.
Ironically, Google does have video of Kenny Gong, the master who taught my teacher and who has since passed away. But, apparently the vids were posted without permission and so, I'm kind of leery about re-posting