Carmichael Training Systems has video and audio workouts for ipods. I downloaded a couple of the "Do the Tour, Stay at Home" audio workouts for when I'm traveling and working out in hotel fitness centers.
The CTS workouts are ok. The intervals are typically on the long side (5-6 minutes) in the workouts that I downloaded. So the whole workout tends to last for more than an hour. There are voice overs and countdowns by Chris Carmichael and Bob Roll -- but there is also alot of indirect advertising for various products (like PowerGel) and you don't get a choice of music.
I looked through the descriptions of some of the video workout intervals and jotted them down and am going to use those as templates and get my own music to go along with each interval.
-traveller
"It never gets easier, you just go faster." -- Greg LeMond