Ok, it's an hour long, so longer than you are looking for, but I think there are some pre-mixes, and it really fits the FUN bill, Amy Bento's new Kickbox surge dvd is super fun with great music.
What other options are there for advanced low-impact cardio? My knees are really, really starting to have problems. I have LI circuit and LI step, but I think that I might need to abandon the step altogether.
I'm doing STS and I'm using CC for most of my cardio workouts. I do them on an elliptical. I also do kettlebell workouts and many of them have a cardio effect. I have no idea what else to recommend, but then I typically hate cardio and prefer to do it on machines. What about some kickbox DVD's? Powerstrikes, Kimberly Spreen, Amy Bento, and Tracey Staehle all seem to be popular.