At the moment my running playlist mainstays are:
lady gaga (seriously, marry the night album, yes)
nicki minaj (that girl got some beats)
HANSON ( they are still a band and have released many new albums since mmmbop, even though that song is still one of my favs)
Basshunter (love that Swedish eurodance)
Although I completely love being able to jam during training runs, I am still pretty opposed to being plugged in on race day. When competing I think its really essential to be completely aware of your surroundings and being able to continually read your body cues throughout the race that you might not tap into if your brain is being distracted. Foot strikes, breathing, and hearing someone coming up on your tail are details that you may be unaware of if you are headbanging to favorite song. Not to mention a lot of races are banning the use of music players because they cause unnecessary collisions with your fellow competitors.
So, keep rocking out to your favorite songs during your training tempos and your long runs (unless you are on busy roads, cars can sneak up on you too), but perhaps leave the ear buds at home on race day. You can never underestimate the power of that certain rap song to get you out the door and on your way to a great workout.