What's popular with American teenage boys today?

I'm an American, but I've been out of the country in Japan for 8 years. I have a pretty good idea of what 13-15 year old girls are into (Lady GaGa, Selena Gomez, Justin Bieber, Katy Perry, etc.) but I honestly have no idea what's popular with boys these days. I'm asking this because I need to put together an presentation on current American pop culture. Any leads appreciated. Thanks!