I would like to second CardioCoach for gym workouts. They are EXCELLENT workouts and they can be as tough as you make them. They can be used on any cardio machine (or even outside if you run) but I like them best for the elliptical or the bike. You can get them on CD if you have a Discman, or you can download the MP3's.

http://www.cardiocoach.com/

Spin classes are also a good option if you have good instructors (I've had good and bad and it really can make or break a class).

For someone who asked, I don't have an Ipod, I use a Rio Forge Sport MP3 player. I bought an extra card, and now my player holds 1.25 G of music which is plenty for me. It's also small enough to stay out of the way and it's super sturdy. Love it! In general, there are two basic types of MP3 players...flash players and hard-drive players. A flash player is sturdier (won't skip if dropped) and it has less working parts to damage, but it's limite to the size of the card it uses (either installed, or additional). A hard-drive player will hold a LOT more, but it works kind of like a hard-drive in a computer and can be more easily damaged (though they make them pretty tough these days!). Flash players are generally cheaper, too.

Came back to add this link:
http://www.rioaudio.com/shop/_templa....asp?model=265