Hey Jess!,
I do a lot of yoga and pilates DVDs.
I actually really like the MTV Pilates and Yoga series. They are both done by they same person. The MTV pilates is broken up in to two 20-25 minute segments; one focusing on your upper body and the other on your lower body. There are two yoga ones - Yoga and Power Yoga. I do both, but Power Yoga is significantly harder!
I do the Rael DVD (from Melissa's post) sometimes, too. It's a full hour but a little slower and more focused on technique than the MTV ones which move a bit faster. You will feel your abs in the morning after this one, though!
Good luck!
Kris
26 w/ CF