Haven't I heard this song before?

I recently started teaching spin and yoga classes. The yoga I like, the spin...well it's just something to add to my repertoire I guess. For the past month, probably longer, I've been using the same play list for my spin class. There's only one regular attendee in the class, the others come and go so I figured I didn't really need to change the music for just that one person (and I was lazy). The other day I added a couple new songs on top of the old playlist and the student immediately perked up and said "oh, new music!". I sheepishly thought, "darn, she really has noticed the same stuff over and over, maybe I better change it". I put together a new play list which I think is pretty good but I should get another one going too. I have lots of music to choose from but still would like a little inspiration, so, what are your recommendations for work out music?