MusicMoose wants "to provide the world with free, useful music lessons, and a community based site to help back it all up." The site contains hundreds of free video music lessons (often containing notation and/or tablature) with a distinct focus on acoustic and bluegrass music, all taught by some pretty badass pickers (including the astonishingly good mandolin shredder Anthony Hannigan). There are also obligatory but very useful forums. Takeaway: the whole thing is free and you don't have to register to watch the lessons.
In 1961, on the Martha White Show, seven year-old mandolin prodigy Ricky Skaggs performs two songs with Flatt & Scruggs. "Ruby" and "Foggy Mountain Special". [both songs direct to youtube]