Wikisapces: "Which is why we created our brand-new YouTube channel for all our video tours and instructional videos. Not only because it gives us a handy place to share tips and instructions that might be too confusing to describe in just words, but because it lets you, our users, share these videos with your members."
I composed a list of some general Social Networking Sites that children often flock to from my experience (you probably heard of them already):
• Facebook (minimum age requirement: 13)
• Twitter (minimum age requirement: None)
• Google+ (minimum age requirement: 18)
• MySpace (minimum age requirement: 13)
• YouTube (minimum age requirement: 13)
A bit outdated but good overview of social media safety tips for parents (but applicable to teachers too). Also outlines age minimums for accounts on the most popular site (Facebook=13, Twitter=none, etc)