Well as this was merged with the "music you're listening to at the gym" thread, I thought I might comment, but since I've now got a 512MB card in my MP3 player and there's over 50 tracks on there which I stick on Random Play, it's a bit difficult to say
Most of it is rock/ heavy rock stuff, although with wierd irony, it picked "Night Boat to Cairo" when I was on the Rowing Machine...!