Music is definitely a motivator. I love cranking up my iPod and running to the beat of my favorite play list. Yep, the music keeps me moving.
What I am not a fan of is the headphones that came with my iPod. They always fall out of my ears when I am out running. Thankfully Nike has come up with a comfy alternative, the Vapor Headphones. They have an adjustable hinge so the headphones fit snug against the back of your ear and they stay put.
I also like that they're lightweight and waterproof, so you can sweat up a storm or run in rain without worrying about ruining your headphones. They come in white or black, and have a wire extension if you need them to be longer.
Buy them from the Apple Store for $29.95.