Hi Deanie and Cindi!
Trying to narrow down my CC workouts to 2 or 3 favorites is really tough. My favorite often depends on the mood I'm in, and truly, I use and love them ALL. I have to agree with Vilma's advice to get all of them if you can afford it because you'll end up getting them anyway.
Volumes 1 through 4, and 6 offer a good mix of hills and sprints.
If you enjoy running, then Volumes 5 and 7 are MUST HAVES!
If you enjoy hills then you need Volume 8 which is nothing but one big hill climb.
The workouts are progressively more difficult as you go up in the volumes. With each volume, the workouts are longer in duration with longer challenges and shorter rest periods.
Sean gives written descriptions of each workout on his website. Just go here
http://www.cardiocoach.com/miva/merchant.mvc?Screen=CTGY&Store_Code=CCPS&Category_Code=PRO and click on the workout you're interested in, then click on the link for more information. There you will find the complete structure of the workout with the duration of intervals and rest periods laid out for you. HTH and please let us know which ones you choose!
ETA that volumes 1 through 4 may be shorter but that doesn't mean they aren't challenging. You work according to your own perceived exertion, so if you crank up your settings the earlier volumes are pretty intense.
