Now, for some of us, especially on longer runs, we need music to keep motivation, steady beat, etc....but what songs best suit this? Its been proven that occassional treadmill sessions can increase your natural pace because it forces you to keep the higher rhythm....well, music selection can do the same thing.
I discovered the All8 BPM site to calculate your current running pace...try to mimic it. Simply click the white space in the last "touchscreen" line and click your keyboard to determine your running pace. Hopefully you can estimate it pretty well, as I don't think you want to carry around a keyboard outside and run to get an exact BPM pace! Now, you may want to tap a tad higher on the keyboard to get at a pace that is pushing you a bit, for training purposes, but not so fast that you struggle.
Another great option is Jog.fm - you plug your goal mile time into the search engine (or desired BPMs) and it generates a list of songs. Just click through to purchase on iTunes or Amazon! They also have full play lists for the same pace.
Cadence appears to be the nicest version which covers a myriad list of BPM needs. There is an iphone app, a desktop app that reviews and updates your BPM in the iTunes library and they even have a BPM calculator.
Also, check out Podrunner and MotionTraxx both have free workout music downloads available in any BPM.