Amazing resource for tutorials on almost anything you can think of. Access to music, movies, etc.... Easy to navigate, reasonable advertisements, not to spammy. But, there are numerous inappropriate videos that would be disturbing for children.
This youtube video on evaluating resources is terrific. I would just suggest that students beware of the comments if the are able to view them. This video truly gives a great walk through of how students can begin the process of evaluating resources.
It's owned by Google, and anyone can post anything they want, but of course, Google, and any respective companies, can take down those videos. It has many child friendly videos, but you have to be careful, as because people can post whatever they want, they're is some extremely inappropriate content on it as well. Luckily, however, such content is rare.
It's a safe site, you won't get any viruses, that is unless you don't have a firewall of some sort, if that's the case, you'll get a virus from pretty much anywhere.