I've downloaded some Japanese rap songs onto my mp3 player. Specifically, Tokyo Drift, HeartBreaker, and Cho Large - all by the Teriyaki Boyz.

I have to admit, I was surprised at how good they are. I can't understand every word of their songs, but I can understand a lot of it. Japanese is a hard language to make poetry (which is what songs are) with, but they seem to do it without trouble. You have to applaud them for that.