Music
I like listening to music as I run. The vast majority of the time I simply listen to songs at random from my iPod's large library. I get the runner's high fairly easily and when that's kicked in, the music and lyrics pull me in different directions. The randomness is like a washing machine for my mind.
I do, however, have several playlists, and I've included approximations of my three different "speed" (high cadence, motivating) ones here. I use Speed 3 when I'm doing interval training, Speed 9 when I'm running as quickly as I can for a distance anywhere from six miles to thirteen and a half and my Bataan Memorial Death March (BMDM) playlist when I'm doing my Saturday BMDM training or when I'm racing a marathon trying to qualify for the Boston Marathon or otherwise do well for my age.
Although not as fast as Me First and the Gimme Gimmes, I also run fairly quickly to Professor Longhair and the faster tunes of Klezmatics.
My favorite runner's song, however, is Runner's High by the pillows.
Special mention of The Impression That I Get, because I'm sure it isn't good.