For YouTube, use cuteTube. Nice QML interface, integrates well into Harmattan and by buying it, you support community devs (marxian, that is). I think my 2 Euros for it are spent well.
Yep. Marxian did a great job, worth it. But I've yet to buy it... if I hit a Youtube video, does it spring into action? Like say you send me a youtube link in e-mail, does it open up CuteTube?