Where do you find good, upbeat music for group fitness classes?
www.cardiomixes.com (lots of variety on this site and you can hear them first. they even have interval training with whistles/horns)
www.32mixes.com (original artists, lots of different songs, just fun music here)
I make my own mixes with Mixmeister. (http://mixmeister.com/). Their basic program is $50 and easy to use. You can change the BPM (without any chipmunk vocals) and seamlessly blend songs. I mix formats and years and every student finds at least one song to love in each class. I am also inspired by the music and know I give a better class because I enjoy my mixes.