There are several main video sites that I know of--and probably a handful more with which I am still unfamiliar--places like YouTube, Vimeo, and others. But then there are offshoots, like Tangle, that try to cash in on the success of these free video hosting/sharing sites.
With mixed results.
TeacherTube and HomeschoolViewTube are two examples of sites that are, well, floundering. These are niche sites that focus on a particular type of video to get people to congregate there. Here's the problem with these kinds of sites:
There's no need for them.
YouTube, which is more ubiquitous, will host these videos just fine. And then you have the power of Google behind you too. Not that you couldn't host your videos on these other sites... but it doesn't gain you anything to do so. Unless they took off. Which would require people uploading tons of useful content there. And, well, you just can't compete with YouTube's insane amount of content (I heard a rumor it was close to 24 hours of footage every hour... but I can't confirm that so it may just be web hype).
Vimeo, on the other hand, offers you a place to upload huge video files, and so caters to the filmmakers of the world.
Other sites of a more... <cough> questionable nature provide those videos that are not as readily accepted on YouTube. So those have a natural niche as well.
But these other video sites--like those mentioned above--offer nothing new. And that is why they are floundering with only a handful of clips.
Your Media Production Mentor