I have really been enjoying Cardio Coach. It's sort of techno and is specifically geared toward interval training using any method you choose (I use an elliptical). I love it. It lasts about 40 minutes and is very motivating! One of my clients recommended it and she used it to train for a 5K and won in her age category (54). I downloaded it from the website for $13.99. If you choose to look into it, my favorite is volume 3. Just google cardio coach. Aside from that, I like old Hall & Oats, Doors (break on through to the other side), the Who, AC/DC. Yeah, I am definitely dating myself!