JamPlay is doing it big in the guitar world. Their site is a membership service only that broadcasts HD videos with beginners guitar lessons. They have brought guitar lessons with interactivity together… you can even ask questions to the guitar teachers. They have 5-6 guitar teachers to give you a selection in different teaching methods, and that's a big plus.
They teach you with "lessons in sets" and not just putting out a lot of small video clips. They start with the basics like tuning the guitar, finger placement, and some basic chords, moves on to finger-picking, hammer ons, pull offs, palm muting, and a lot more advanced topics as you progress through the lessons. We found this surprisingly good for the overall experience, because you can follow through these lesson sets just how you would with a normal guitar teacher. Biggest thing is, it's cheap as well because they get so many members.