Mine goes through stages. depending on what I need.
Rage Against the Machine - Know Your Enemy or
Limp Bizkit - Break Stuff
To get you up hills or through the last few steps.
Kelly Clarkson - Since You've Been Gone
Blackstreet - No Diggity
General running
Green Day - American Idiot
Dizzee Rascal - Bonkers
To keep my pace up when I'm flagging
Basement Jaxx - Red Alert
Chemical Brothers - Go
When I feel blah or to cheer me up
I always need new music though. It really affects my running.