justin timberlake - bastard
(back to what does help - i find any sort of rock music... the faster the better i suppose so homebound train

anything by iron maiden, some deep purple stuff, a lot of Rainbow stuff, or some Sabbath/DIO music - donnington 87 rocks particularly hard)... what else:
scorps - tokyo tapes
whitesnake - live tokyo 88
springsteen oddly enough (acoustic stuff - i've done that)
my own 65 min prog rock album "reflections"
MSG are good too - i should put them on minidisc
but that being said i don't intend to do more than maybe 1 hour on the running machines and music's not as important for the other machines so it doesn't matter to have a big compilation