I just re-did my gym playlist and I wasn't sure what to put on it because I always had the same old stuff. So I went to Pandora.com (do you use Pandora? It's awesome) and I put in one song that represented the style and tempo I was looking for (for me it was Katy Perry Hot n' cold) and then I got tons of songs by other artists that were perfect for what I wanted. I just jotted down the ones I liked and downloaded them. It worked great!
Some songs that I have on the workout playlist on my iPod currently are: (they are all pretty random as you can tell)Ain't No Mountain High Enough-Marvin GayeViva la Vida-ColdplayBreathless-The CorrsSo Happy Together-The TurtlesCome on Over Baby-Christina AgulieraLove Song-Sara BareillesIn His Kiss-CherDisease-Matchbox 20